Input: arc_ps2 - add support for device tree

Add match table for device tree binding and dts binding doc.

Signed-off-by: Mischa Jonker <mjonker@synopsys.com>
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>

Documentation/devicetree/bindings/serio/snps-arc_ps2.txt

@@ -0,0 +1,16 @@
+* ARC PS/2 driver: PS/2 block used in some ARC FPGA's & nSIM OSCI model
+
+Required properties:
+- compatible		: "snps,arc_ps2"
+- reg			: offset and length (always 0x14) of registers
+- interrupts		: interrupt
+- interrupt-names	: name of interrupt, must be "arc_ps2_irq"
+
+Example:
+
+serio@c9000400 {
+	compatible = "snps,arc_ps2";
+	reg = <0xc9000400 0x14>;
+	interrupts = <13>;
+	interrupt-names = "arc_ps2_irq";
+}