drm: bridge: add DT bindings for TI ths8135

THS8135 is a configurable video DAC. Add DT bindings for this chip.
Signed-off-by: Bartosz Golaszewski <bgolaszewski@baylibre.com>
Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Acked-by: Rob Herring <robh@kernel.org>
Signed-off-by: Archit Taneja <architt@codeaurora.org>
Link: http://patchwork.freedesktop.org/patch/msgid/1481623759-12786-3-git-send-email-bgolaszewski@baylibre.com

Documentation/devicetree/bindings/display/bridge/ti,ths8135.txt

+THS8135 Video DAC
+-----------------
+
+This is the binding for Texas Instruments THS8135 Video DAC bridge.
+
+Required properties:
+
+- compatible: Must be "ti,ths8135"
+
+Required nodes:
+
+This device has two video ports. Their connections are modelled using the OF
+graph bindings specified in Documentation/devicetree/bindings/graph.txt.
+
+- Video port 0 for RGB input
+- Video port 1 for VGA output
+
+Example
+-------
+
+vga-bridge {
+	compatible = "ti,ths8135";
+	#address-cells = <1>;
+	#size-cells = <0>;
+
+	ports {
+		#address-cells = <1>;
+		#size-cells = <0>;
+
+		port@0 {
+			reg = <0>;
+
+			vga_bridge_in: endpoint {
+				remote-endpoint = <&lcdc_out_vga>;
+			};
+		};
+
+		port@1 {
+			reg = <1>;
+
+			vga_bridge_out: endpoint {
+				remote-endpoint = <&vga_con_in>;
+			};
+		};
+	};
+};