serial: pl011: honour serial aliases in device tree

index d3553b5..dc05dd1 100644
@@ -52,6 +52,8 @@
 #include <linux/scatterlist.h>
 #include <linux/delay.h>
 #include <linux/types.h>
+#include <linux/of.h>
+#include <linux/of_device.h>
 #include <linux/pinctrl/consumer.h>
 #include <linux/sizes.h>
 

@@ -1869,6 +1871,38 @@ static struct uart_driver amba_reg = {
 	.cons			= AMBA_CONSOLE,
 };
 
+static int pl011_probe_dt_alias(int index, struct device *dev)
+{
+	struct device_node *np;
+	static bool seen_dev_with_alias = false;
+	static bool seen_dev_without_alias = false;
+	int ret = index;
+
+	if (!IS_ENABLED(CONFIG_OF))
+		return ret;
+
+	np = dev->of_node;
+	if (!np)
+		return ret;
+
+	ret = of_alias_get_id(np, "serial");
+	if (IS_ERR_VALUE(ret)) {
+		seen_dev_without_alias = true;
+		ret = index;
+	} else {
+		seen_dev_with_alias = true;
+		if (ret >= ARRAY_SIZE(amba_ports) || amba_ports[ret] != NULL) {
+			dev_warn(dev, "requested serial port %d  not available.\n", ret);
+			ret = index;
+		}
+	}
+
+	if (seen_dev_with_alias && seen_dev_without_alias)
+		dev_warn(dev, "aliased and non-aliased serial devices found in device tree. Serial port enumeration may be unpredictable.\n");
+
+	return ret;
+}
+
 static int pl011_probe(struct amba_device *dev, const struct amba_id *id)
 {
 	struct uart_amba_port *uap;

@@ -1891,6 +1925,8 @@ static int pl011_probe(struct amba_device *dev, const struct amba_id *id)
 		goto out;
 	}
 
+	i = pl011_probe_dt_alias(i, &dev->dev);
+
 	base = ioremap(dev->res.start, resource_size(&dev->res));
 	if (!base) {
 		ret = -ENOMEM;