Doc/DT: Add DT binding documentation for MIPI DSI CM Panel

Add DT binding documentation for MIPI DSI Command Mode Panel.
Signed-off-by: Tomi Valkeinen <tomi.valkeinen@ti.com>
Reviewed-by: Archit Taneja <archit@ti.com>
Acked-by: Philipp Zabel <p.zabel@pengutronix.de>

Documentation/devicetree/bindings/video/panel-dsi-cm.txt

+Generic MIPI DSI Command Mode Panel
+===================================
+
+Required properties:
+- compatible: "panel-dsi-cm"
+
+Optional properties:
+- label: a symbolic name for the panel
+- reset-gpios: panel reset gpio
+- te-gpios: panel TE gpio
+
+Required nodes:
+- Video port for DSI input
+
+Example
+-------
+
+lcd0: display {
+	compatible = "tpo,taal", "panel-dsi-cm";
+	label = "lcd0";
+
+	reset-gpios = <&gpio4 6 GPIO_ACTIVE_HIGH>;
+
+	port {
+		lcd0_in: endpoint {
+			remote-endpoint = <&dsi1_out_ep>;
+		};
+	};
+};