diff --git a/Documentation/ABI/stable/sysfs-driver-aspeed-uart-routing b/Documentation/ABI/stable/sysfs-driver-aspeed-uart-routing
new file mode 100644
index 000000000000..5068737d9c12
--- /dev/null
+++ b/Documentation/ABI/stable/sysfs-driver-aspeed-uart-routing
@@ -0,0 +1,14 @@
+What:		/sys/bus/platform/drivers/aspeed-uart-routing/*/io*
+Date:		August 2018
+Contact:	Oskar Senft <osk@google.com>
+Description:	Configures the input source for the specific physical
+		serial I/O port.
+Users:		OpenBMC.  Proposed changes should be mailed to
+		openbmc@lists.ozlabs.org
+
+What:		/sys/bus/platform/drivers/aspeed-uart-routing/*/uart*
+Date:		August 2018
+Contact:	Oskar Senft <osk@google.com>
+Description:	Configures the input source for the specific UART.
+Users:		OpenBMC.  Proposed changes should be mailed to
+		openbmc@lists.ozlabs.org
diff --git a/Documentation/misc-devices/aspeed-uart-routing.txt b/Documentation/misc-devices/aspeed-uart-routing.txt
new file mode 100644
index 000000000000..cf1c2a466875
--- /dev/null
+++ b/Documentation/misc-devices/aspeed-uart-routing.txt
@@ -0,0 +1,49 @@
+Kernel driver aspeed-uart-routing
+=================================
+
+Supported chips:
+ASPEED AST2500/AST2600
+
+Author:
+Google LLC
+
+Description
+-----------
+
+The Aspeed AST2500/AST2600 allows to dynamically route the inputs for the
+built-in UARTS and physical serial I/O ports.
+
+This allows, for example, to connect the output of UART to another UART.
+This can be used to enable host<->BMC communication via UARTs, e.g. to allow
+access to the host's serial console.
+
+This driver is for the BMC side. The sysfs files allow the BMC userspace
+which owns the system configuration policy, to configure how UARTs and
+physical serial I/O ports are routed.
+
+The driver provides the following files in sysfs:
+uart1		Configure the input signal to UART1.
+uart2		Configure the input signal to UART2.
+uart3		Configure the input signal to UART3.
+uart4		Configure the input signal to UART4.
+uart5		Configure the input signal to UART5.
+io1		Configure the input signal to physical serial port 1.
+io2		Configure the input signal to physical serial port 2.
+io3		Configure the input signal to physical serial port 3.
+io4		Configure the input signal to physical serial port 4.
+io5		Configure the input signal to physical serial port 5.
+
+When read, each file shows the list of available options with the currently
+selected option marked by square brackets "[]". The list of available options
+depends on the selected file.
+
+Example:
+$ cat /sys/bus/platform/drivers/aspeed-uart-routing/*.uart_routing/uart1
+[io1] io2 io3 io4 uart2 uart3 uart4 io6
+
+In this case, UART1 gets its input signal from IO1 (physical serial port 1).
+
+$ echo -n "uart3" \
+  >/sys/bus/platform/drivers/aspeed-uart-routing/*.uart_routing/uart1
+$ cat /sys/bus/platform/drivers/aspeed-uart-routing/*.uart_routing/uart1
+io1 io2 io3 io4 uart2 [uart3] uart4 io6
diff --git a/drivers/misc/Kconfig b/drivers/misc/Kconfig
index d8626a0d3e31..48a519c59bdf 100644
--- a/drivers/misc/Kconfig
+++ b/drivers/misc/Kconfig
@@ -451,6 +451,12 @@ config MCTP_LPC
 	  Implements the MCTP LPC binding via KCS LPC IO cycles for control and
           LPC FWH cycles for data
 
+config ASPEED_UART_ROUTING
+	tristate "Aspeed ast2500 UART routing control"
+	help
+	  If you want to configure UART routing on Aspeed BMC platforms, enable
+	  this option.
+
 config MISC_RTSX
 	tristate
 	default MISC_RTSX_PCI || MISC_RTSX_USB
diff --git a/drivers/misc/Makefile b/drivers/misc/Makefile
index 183970192ced..4e67e21c2e65 100644
--- a/drivers/misc/Makefile
+++ b/drivers/misc/Makefile
@@ -60,3 +60,4 @@ obj-$(CONFIG_XILINX_SDFEC)	+= xilinx_sdfec.o
 obj-$(CONFIG_NPCM7XX_LPC_BPC)	+= npcm7xx-lpc-bpc.o
 obj-$(CONFIG_NPCM7XX_PCI_MBOX)	+= npcm7xx-pci-mbox.o
 obj-$(CONFIG_MCTP_LPC)		+= mctp-lpc.o
+obj-$(CONFIG_ASPEED_UART_ROUTING) += aspeed-uart-routing.o
diff --git a/drivers/misc/aspeed-uart-routing.c b/drivers/misc/aspeed-uart-routing.c
new file mode 100644
index 000000000000..21ef5d98c317
--- /dev/null
+++ b/drivers/misc/aspeed-uart-routing.c
@@ -0,0 +1,383 @@
+/*
+ * UART Routing driver for Aspeed AST2500
+ *
+ * Copyright (c) 2018 Google LLC
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * version 2 as published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU General Public License for more details.
+ */
+#include <linux/device.h>
+#include <linux/module.h>
+#include <linux/of_address.h>
+#include <linux/of_platform.h>
+
+/* The Aspeed AST2500 allows to dynamically route the inputs for the built-in
+ * UARTS and physical serial I/O ports.
+ *
+ * This allows, for example, to connect the output of UART to another UART.
+ * This can be used to enable host<->BMC communication via UARTs, e.g. to allow
+ * access to the host's serial console.
+ *
+ * This driver is for the BMC side. The sysfs files allow the BMC userspace
+ * which owns the system configuration policy, to configure how UARTs and
+ * physical serial I/O ports are routed.
+ */
+
+#define ASPEED_HICRA_IO1	"io1"
+#define ASPEED_HICRA_IO2	"io2"
+#define ASPEED_HICRA_IO3	"io3"
+#define ASPEED_HICRA_IO4	"io4"
+#define ASPEED_HICRA_IO5	"io5"
+#define ASPEED_HICRA_IO6	"io6"
+#define ASPEED_HICRA_UART1	"uart1"
+#define ASPEED_HICRA_UART2	"uart2"
+#define ASPEED_HICRA_UART3	"uart3"
+#define ASPEED_HICRA_UART4	"uart4"
+#define ASPEED_HICRA_UART5	"uart5"
+
+struct aspeed_uart_routing {
+	struct device		*dev;
+	void __iomem		*regs;
+	spinlock_t		lock;
+};
+
+struct aspeed_uart_routing_selector {
+	struct device_attribute	dev_attr;
+	int				shift;
+	int				mask;
+	const char * const options[];
+};
+
+#define to_routing_selector(_dev_attr)					\
+	container_of(_dev_attr, struct aspeed_uart_routing_selector, dev_attr)
+
+
+static ssize_t aspeed_uart_routing_show(struct device *dev,
+					struct device_attribute *attr,
+					char *buf);
+
+static ssize_t aspeed_uart_routing_store(struct device *dev,
+					 struct device_attribute *attr,
+					 const char *buf, size_t count);
+
+#define ROUTING_ATTR(_name) {						\
+	.attr = {.name = _name,					\
+		 .mode = VERIFY_OCTAL_PERMISSIONS(S_IWUSR | S_IRUGO) }, \
+	.show = aspeed_uart_routing_show,				\
+	.store = aspeed_uart_routing_store,				\
+}
+
+static struct aspeed_uart_routing_selector uart5_sel = {
+	.dev_attr = ROUTING_ATTR(ASPEED_HICRA_UART5),
+	.shift = 28,
+	.mask = 0xf,
+	.options = {
+		    ASPEED_HICRA_IO5,   // 0
+		    ASPEED_HICRA_IO1,   // 1
+		    ASPEED_HICRA_IO2,   // 2
+		    ASPEED_HICRA_IO3,   // 3
+		    ASPEED_HICRA_IO4,   // 4
+		    ASPEED_HICRA_UART1, // 5
+		    ASPEED_HICRA_UART2, // 6
+		    ASPEED_HICRA_UART3, // 7
+		    ASPEED_HICRA_UART4, // 8
+		    ASPEED_HICRA_IO6,   // 9
+		    NULL,               // NULL termination
+		    },
+};
+
+static struct aspeed_uart_routing_selector uart4_sel = {
+	.dev_attr = ROUTING_ATTR(ASPEED_HICRA_UART4),
+	.shift = 25,
+	.mask = 0x7,
+	.options = {
+		    ASPEED_HICRA_IO4,   // 0
+		    ASPEED_HICRA_IO1,   // 1
+		    ASPEED_HICRA_IO2,   // 2
+		    ASPEED_HICRA_IO3,   // 3
+		    ASPEED_HICRA_UART1, // 4
+		    ASPEED_HICRA_UART2, // 5
+		    ASPEED_HICRA_UART3, // 6
+		    ASPEED_HICRA_IO6,   // 7
+		    NULL,               // NULL termination
+	},
+};
+
+static struct aspeed_uart_routing_selector uart3_sel = {
+	.dev_attr = ROUTING_ATTR(ASPEED_HICRA_UART3),
+	.shift = 22,
+	.mask = 0x7,
+	.options = {
+		    ASPEED_HICRA_IO3,   // 0
+		    ASPEED_HICRA_IO4,   // 1
+		    ASPEED_HICRA_IO1,   // 2
+		    ASPEED_HICRA_IO2,   // 3
+		    ASPEED_HICRA_UART4, // 4
+		    ASPEED_HICRA_UART1, // 5
+		    ASPEED_HICRA_UART2, // 6
+		    ASPEED_HICRA_IO6,   // 7
+		    NULL,               // NULL termination
+		    },
+};
+
+static struct aspeed_uart_routing_selector uart2_sel = {
+	.dev_attr = ROUTING_ATTR(ASPEED_HICRA_UART2),
+	.shift = 19,
+	.mask = 0x7,
+	.options = {
+		    ASPEED_HICRA_IO2,   // 0
+		    ASPEED_HICRA_IO3,   // 1
+		    ASPEED_HICRA_IO4,   // 2
+		    ASPEED_HICRA_IO1,   // 3
+		    ASPEED_HICRA_UART3, // 4
+		    ASPEED_HICRA_UART4, // 5
+		    ASPEED_HICRA_UART1, // 6
+		    ASPEED_HICRA_IO6,   // 7
+		    NULL,               // NULL termination
+		    },
+};
+
+static struct aspeed_uart_routing_selector uart1_sel = {
+	.dev_attr = ROUTING_ATTR(ASPEED_HICRA_UART1),
+	.shift = 16,
+	.mask = 0x7,
+	.options = {
+		    ASPEED_HICRA_IO1,   // 0
+		    ASPEED_HICRA_IO2,   // 1
+		    ASPEED_HICRA_IO3,   // 2
+		    ASPEED_HICRA_IO4,   // 3
+		    ASPEED_HICRA_UART2, // 4
+		    ASPEED_HICRA_UART3, // 5
+		    ASPEED_HICRA_UART4, // 6
+		    ASPEED_HICRA_IO6,   // 7
+		    NULL,               // NULL termination
+		    },
+};
+
+static struct aspeed_uart_routing_selector io5_sel = {
+	.dev_attr = ROUTING_ATTR(ASPEED_HICRA_IO5),
+	.shift = 12,
+	.mask = 0x7,
+	.options = {
+		    ASPEED_HICRA_UART5, // 0
+		    ASPEED_HICRA_UART1, // 1
+		    ASPEED_HICRA_UART2, // 2
+		    ASPEED_HICRA_UART3, // 3
+		    ASPEED_HICRA_UART4, // 4
+		    ASPEED_HICRA_IO1,   // 5
+		    ASPEED_HICRA_IO3,   // 6
+		    ASPEED_HICRA_IO6,   // 7
+		    NULL,               // NULL termination
+		    },
+};
+
+static struct aspeed_uart_routing_selector io4_sel = {
+	.dev_attr = ROUTING_ATTR(ASPEED_HICRA_IO4),
+	.shift = 9,
+	.mask = 0x7,
+	.options = {
+		    ASPEED_HICRA_UART4, // 0
+		    ASPEED_HICRA_UART5, // 1
+		    ASPEED_HICRA_UART1, // 2
+		    ASPEED_HICRA_UART2, // 3
+		    ASPEED_HICRA_UART3, // 4
+		    ASPEED_HICRA_IO1,   // 5
+		    ASPEED_HICRA_IO2,   // 6
+		    ASPEED_HICRA_IO6,   // 7
+		    NULL,               // NULL termination
+		    },
+};
+
+static struct aspeed_uart_routing_selector io3_sel = {
+	.dev_attr = ROUTING_ATTR(ASPEED_HICRA_IO3),
+	.shift = 6,
+	.mask = 0x7,
+	.options = {
+		    ASPEED_HICRA_UART3, // 0
+		    ASPEED_HICRA_UART4, // 1
+		    ASPEED_HICRA_UART5, // 2
+		    ASPEED_HICRA_UART1, // 3
+		    ASPEED_HICRA_UART2, // 4
+		    ASPEED_HICRA_IO1,   // 5
+		    ASPEED_HICRA_IO2,   // 6
+		    ASPEED_HICRA_IO6,   // 7
+		    NULL,               // NULL termination
+		    },
+};
+
+static struct aspeed_uart_routing_selector io2_sel = {
+	.dev_attr = ROUTING_ATTR(ASPEED_HICRA_IO2),
+	.shift = 3,
+	.mask = 0x7,
+	.options = {
+		    ASPEED_HICRA_UART2, // 0
+		    ASPEED_HICRA_UART3, // 1
+		    ASPEED_HICRA_UART4, // 2
+		    ASPEED_HICRA_UART5, // 3
+		    ASPEED_HICRA_UART1, // 4
+		    ASPEED_HICRA_IO3,   // 5
+		    ASPEED_HICRA_IO4,   // 6
+		    ASPEED_HICRA_IO6,   // 7
+		    NULL,               // NULL termination
+		    },
+};
+
+static struct aspeed_uart_routing_selector io1_sel = {
+	.dev_attr = ROUTING_ATTR(ASPEED_HICRA_IO1),
+	.shift = 0,
+	.mask = 0x7,
+	.options = {
+		    ASPEED_HICRA_UART1, // 0
+		    ASPEED_HICRA_UART2, // 1
+		    ASPEED_HICRA_UART3, // 2
+		    ASPEED_HICRA_UART4, // 3
+		    ASPEED_HICRA_UART5, // 4
+		    ASPEED_HICRA_IO3,   // 5
+		    ASPEED_HICRA_IO4,   // 6
+		    ASPEED_HICRA_IO6,   // 7
+		    NULL,               // NULL termination
+		    },
+};
+
+
+static struct attribute *aspeed_uart_routing_attrs[] = {
+	&uart1_sel.dev_attr.attr,
+	&uart2_sel.dev_attr.attr,
+	&uart3_sel.dev_attr.attr,
+	&uart4_sel.dev_attr.attr,
+	&uart5_sel.dev_attr.attr,
+	&io1_sel.dev_attr.attr,
+	&io2_sel.dev_attr.attr,
+	&io3_sel.dev_attr.attr,
+	&io4_sel.dev_attr.attr,
+	&io5_sel.dev_attr.attr,
+	NULL,
+};
+
+static const struct attribute_group aspeed_uart_routing_attr_group = {
+	.attrs = aspeed_uart_routing_attrs,
+};
+
+static ssize_t aspeed_uart_routing_show(struct device *dev,
+					struct device_attribute *attr,
+					char *buf)
+{
+	struct aspeed_uart_routing *uart_routing = dev_get_drvdata(dev);
+	struct aspeed_uart_routing_selector *sel = to_routing_selector(attr);
+	int val, pos, len;
+
+	val = (readl(uart_routing->regs) >> sel->shift) & sel->mask;
+
+	len = 0;
+	for (pos = 0; sel->options[pos] != NULL; ++pos) {
+		if (pos == val) {
+			len += snprintf(buf + len, PAGE_SIZE - 1 - len,
+					"[%s] ", sel->options[pos]);
+		} else {
+			len += snprintf(buf + len, PAGE_SIZE - 1 - len,
+					"%s ", sel->options[pos]);
+		}
+	}
+
+	if (val >= pos) {
+		len += snprintf(buf + len, PAGE_SIZE - 1 - len,
+				"[unknown(%d)]", val);
+	}
+
+	len += snprintf(buf + len, PAGE_SIZE - 1 - len, "\n");
+
+	return len;
+}
+
+static ssize_t aspeed_uart_routing_store(struct device *dev,
+					 struct device_attribute *attr,
+					 const char *buf, size_t count)
+{
+	struct aspeed_uart_routing *uart_routing = dev_get_drvdata(dev);
+	struct aspeed_uart_routing_selector *sel = to_routing_selector(attr);
+	int val;
+	u32 reg;
+
+	val = match_string(sel->options, -1, buf);
+	if (val < 0) {
+		dev_err(dev, "invalid value \"%s\"\n", buf);
+		return -EINVAL;
+	}
+
+	spin_lock(&uart_routing->lock);
+	reg = readl(uart_routing->regs);
+	// Zero out existing value in specified bits.
+	reg &= ~(sel->mask << sel->shift);
+	// Set new value in specified bits.
+	reg |= (val & sel->mask) << sel->shift;
+	writel(reg, uart_routing->regs);
+	spin_unlock(&uart_routing->lock);
+
+	return count;
+}
+
+static int aspeed_uart_routing_probe(struct platform_device *pdev)
+{
+	struct aspeed_uart_routing *uart_routing;
+	struct resource *res;
+	int rc;
+
+	uart_routing = devm_kzalloc(&pdev->dev,
+				    sizeof(*uart_routing),
+				    GFP_KERNEL);
+	if (!uart_routing)
+		return -ENOMEM;
+
+	spin_lock_init(&uart_routing->lock);
+	uart_routing->dev = &pdev->dev;
+
+	res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
+	uart_routing->regs = devm_ioremap_resource(&pdev->dev, res);
+	if (IS_ERR(uart_routing->regs))
+		return PTR_ERR(uart_routing->regs);
+
+	rc = sysfs_create_group(&uart_routing->dev->kobj,
+				&aspeed_uart_routing_attr_group);
+	if (rc < 0)
+		return rc;
+
+	platform_set_drvdata(pdev, uart_routing);
+
+	return 0;
+}
+
+static int aspeed_uart_routing_remove(struct platform_device *pdev)
+{
+	struct aspeed_uart_routing *uart_routing = platform_get_drvdata(pdev);
+
+	sysfs_remove_group(&uart_routing->dev->kobj,
+			   &aspeed_uart_routing_attr_group);
+
+	return 0;
+}
+
+static const struct of_device_id aspeed_uart_routing_table[] = {
+	{ .compatible = "aspeed,ast2500-uart-routing" },
+	{ },
+};
+
+static struct platform_driver aspeed_uart_routing_driver = {
+	.driver = {
+		.name = "aspeed-uart-routing",
+		.of_match_table = aspeed_uart_routing_table,
+	},
+	.probe = aspeed_uart_routing_probe,
+	.remove = aspeed_uart_routing_remove,
+};
+
+module_platform_driver(aspeed_uart_routing_driver);
+
+MODULE_AUTHOR("Oskar Senft <osk@google.com>");
+MODULE_LICENSE("GPL v2");
+MODULE_DESCRIPTION("Driver to configure Aspeed UART routing");
