tty: serial: msm_serial: document DT alias

Update devicetree binding for msm_serial to reflect msm_serial_probe()
getting line id (port number) from the serialN alias.
Signed-off-by: Frank Rowand <frank.rowand@sonymobile.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Documentation/devicetree/bindings/serial/qcom,msm-uartdm.txt

@@ -27,11 +27,16 @@ Optional properties:
 - dmas: Should contain dma specifiers for transmit and receive channels
 - dma-names: Should contain "tx" for transmit and "rx" for receive channels
 
+Note: Aliases may be defined to ensure the correct ordering of the UARTs.
+The alias serialN will result in the UART being assigned port N.  If any
+serialN alias exists, then an alias must exist for each enabled UART.  The
+serialN aliases should be in a .dts file instead of in a .dtsi file.
+
 Examples:
 
-A uartdm v1.4 device with dma capabilities.
+- A uartdm v1.4 device with dma capabilities.
 
-serial@f991e000 {
+	serial@f991e000 {
 		compatible = "qcom,msm-uartdm-v1.4", "qcom,msm-uartdm";
 		reg = <0xf991e000 0x1000>;
 		interrupts = <0 108 0x0>;
@@ -39,15 +44,35 @@ serial@f991e000 {
 		clock-names = "core", "iface";
 		dmas = <&dma0 0>, <&dma0 1>;
 		dma-names = "tx", "rx";
-};
+	};
 
-A uartdm v1.3 device without dma capabilities and part of a GSBI complex.
+- A uartdm v1.3 device without dma capabilities and part of a GSBI complex.
 
-serial@19c40000 {
+	serial@19c40000 {
 		compatible = "qcom,msm-uartdm-v1.3", "qcom,msm-uartdm";
 		reg = <0x19c40000 0x1000>,
 		<0x19c00000 0x1000>;
 		interrupts = <0 195 0x0>;
 		clocks = <&gsbi5_uart_cxc>, <&gsbi5_ahb_cxc>;
 		clock-names = "core", "iface";
-};
+	};
+
+- serialN alias.
+
+	aliases {
+		serial0 = &uarta;
+		serial1 = &uartc;
+		serial2 = &uartb;
+	};
+
+	uarta: serial@12490000 {
+		status = "ok";
+	};
+
+	uartb: serial@16340000 {
+		status = "ok";
+	};
+
+	uartc: serial@1a240000 {
+		status = "ok";
+	};