[media] Documentation: devicetree: Add document bindings for mtk-cir

This patch adds documentation for devicetree bindings for
consumer Mediatek IR controller.
Signed-off-by: Sean Wang <sean.wang@mediatek.com>
Acked-by: Rob Herring <robh@kernel.org>
Signed-off-by: Sean Young <sean@mess.org>
Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>

Documentation/devicetree/bindings/media/mtk-cir.txt

+Device-Tree bindings for Mediatek consumer IR controller
+found in Mediatek SoC family
+
+Required properties:
+- compatible	    : "mediatek,mt7623-cir"
+- clocks	    : list of clock specifiers, corresponding to
+		      entries in clock-names property;
+- clock-names	    : should contain "clk" entries;
+- interrupts	    : should contain IR IRQ number;
+- reg		    : should contain IO map address for IR.
+
+Optional properties:
+- linux,rc-map-name : see rc.txt file in the same directory.
+
+Example:
+
+cir: cir@10013000 {
+	compatible = "mediatek,mt7623-cir";
+	reg = <0 0x10013000 0 0x1000>;
+	interrupts = <GIC_SPI 87 IRQ_TYPE_LEVEL_LOW>;
+	clocks = <&infracfg CLK_INFRA_IRRX>;
+	clock-names = "clk";
+	linux,rc-map-name = "rc-rc6-mce";
+};