arm: vt8500: doc: Add device tree bindings for arch-vt8500 devices

Bindings for gpio, interrupt controller, power management controller,
timer, realtime clock, serial uart, ehci and uhci controllers and
framebuffer controllers used on the arch-vt8500 platform.

Framebuffer binding also specifies a 'display' node which is required
for determining the lcd panel data.

Signed-off-by: Tony Prisk <linux@prisktech.co.nz>

Documentation/devicetree/bindings/rtc/via,vt8500-rtc.txt

@@ -0,0 +1,15 @@
+VIA/Wondermedia VT8500 Realtime Clock Controller
+-----------------------------------------------------
+
+Required properties:
+- compatible : "via,vt8500-rtc"
+- reg : Should contain 1 register ranges(address and length)
+- interrupts : alarm interrupt
+
+Example:
+
+	rtc@d8100000 {
+		compatible = "via,vt8500-rtc";
+		reg = <0xd8100000 0x10000>;
+		interrupts = <48>;
+	};