serial: vt8500: Add missing binding document for arch-vt8500 serial driver.

The binding document for the vt8500/wm8xxx SoC UART driver is missing.
This patch adds the binding document.

Signed-off-by: Tony Prisk <linux@prisktech.co.nz>
Signed-off-by: Rob Herring <robh@kernel.org>

diff --git a/Documentation/devicetree/bindings/serial/vt8500-uart.txt b/Documentation/devicetree/bindings/serial/vt8500-uart.txt
new file mode 100644 (file)
index 0000000..795c393
--- /dev/null
+++ b/Documentation/devicetree/bindings/serial/vt8500-uart.txt
@@ -0,0 +1,26 @@
+* VIA VT8500 and WonderMedia WM8xxx UART Controller
+
+Required properties:
+- compatible: should be "via,vt8500-uart"
+
+- reg: base physical address of the controller and length of memory mapped
+       region.
+
+- interrupts: hardware interrupt number
+
+- clocks: shall be the input parent clock phandle for the clock. This should
+       be the 24Mhz reference clock.
+
+Aliases may be defined to ensure the correct ordering of the uarts.
+
+Example:
+       aliases {
+               serial0 = &uart0;
+       };
+
+       uart0: serial@d8200000 {
+               compatible = "via,vt8500-uart";
+               reg = <0xd8200000 0x1040>;
+               interrupts = <32>;
+               clocks = <&clkuart0>;
+       };