serial: efm32: properly namespace location property

While reviewing an i2c driver for efm32 that needs a similar property
Wolfram Sang pointed out that "location" is a too generic name for something
that is efm32 specific. So add an appropriate namespace and fall back to the
generic name in case of failure.
Signed-off-by: NUwe Kleine-König <u.kleine-koenig@pengutronix.de>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>

Documentation/devicetree/bindings/serial/efm32-uart.txt

@@ -6,7 +6,7 @@ Required properties:
 - interrupts : Should contain uart interrupt
 
 Optional properties:
-- location : Decides the location of the USART I/O pins.
+- efm32,location : Decides the location of the USART I/O pins.
   Allowed range : [0 .. 5]
   Default: 0
 
@@ -16,5 +16,5 @@ uart@0x4000c400 {
 	compatible = "efm32,uart";
 	reg = <0x4000c400 0x400>;
 	interrupts = <15>;
-	location = <0>;
+	efm32,location = <0>;
 };

drivers/tty/serial/efm32-uart.c

@@ -671,7 +671,10 @@ static int efm32_uart_probe_dt(struct platform_device *pdev,
 	if (!np)
 		return 1;
 
-	ret = of_property_read_u32(np, "location", &location);
+	ret = of_property_read_u32(np, "efm32,location", &location);
+	if (ret)
+		/* fall back to old and (wrongly) generic property "location" */
+		ret = of_property_read_u32(np, "location", &location);
 	if (!ret) {
 		if (location > 5) {
 			dev_err(&pdev->dev, "invalid location\n");