dt-bindings: display: Document FriendlyELEC HD702E LCD panel

FriendlyELEC HD702E 800x1280 LCD panel

HD702E lcd is FriendlyELEC developed eDP LCD panel with 800x1280

resolution. It has built in Goodix, GT9271 captive touchscreen

with backlight adjustable via PWM.

Required properties:

- compatible: should be "friendlyarm,hd702e"

- power-supply: regulator to provide the supply voltage

Optional properties:

- backlight: phandle of the backlight device attached to the panel

Optional nodes:

- Video port for LCD panel input.

This binding is compatible with the simple-panel binding, which is specified

in simple-panel.txt in this directory.

Example:

	panel {

		compatible ="friendlyarm,hd702e", "simple-panel";

		backlight = <&backlight>;

		power-supply = <&vcc3v3_sys>;

		port {

			panel_in_edp: endpoint {

				remote-endpoint = <&edp_out_panel>;

			};

		};

	};