serial: lantiq: Get serial id from dts

Get serial id from dts, also keep backward compatible when dts is not
updated.
Signed-off-by: Songjun Wu <songjun.wu@linux.intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/tty/serial/lantiq.c

@@ -688,7 +688,7 @@ lqasc_probe(struct platform_device *pdev)
 	struct ltq_uart_port *ltq_port;
 	struct uart_port *port;
 	struct resource *mmres, irqres[3];
-	int line = 0;
+	int line;
 	int ret;
 
 	mmres = platform_get_resource(pdev, IORESOURCE_MEM, 0);
@@ -699,9 +699,20 @@ lqasc_probe(struct platform_device *pdev)
 		return -ENODEV;
 	}
 
-	/* check if this is the console port */
-	if (mmres->start != CPHYSADDR(LTQ_EARLY_ASC))
-		line = 1;
+	/* get serial id */
+	line = of_alias_get_id(node, "serial");
+	if (line < 0) {
+		if (IS_ENABLED(CONFIG_LANTIQ)) {
+			if (mmres->start == CPHYSADDR(LTQ_EARLY_ASC))
+				line = 0;
+			else
+				line = 1;
+		} else {
+			dev_err(&pdev->dev, "failed to get alias id, errno %d\n",
+				line);
+			return line;
+		}
+	}
 
 	if (lqasc_port[line]) {
 		dev_err(&pdev->dev, "port %d already allocated\n", line);