dt-bindings: meson: add specific simplefb bindings

Meson specific Simple Framebuffer bindings

This binding documents meson specific extensions to the simple-framebuffer

bindings. The meson simplefb u-boot code relies on the devicetree containing

pre-populated simplefb nodes.

These extensions are intended so that u-boot can select the right node based

on which pipeline is being used. As such they are solely intended for

firmware / bootloader use, and the OS should ignore them.

Required properties:

- compatible: "amlogic,simple-framebuffer", "simple-framebuffer"

- amlogic,pipeline, one of:

  "vpu-cvbs"

  "vpu-hdmi"

Example:

chosen {

	#address-cells = <2>;

	#size-cells = <2>;

	ranges;

	simplefb_hdmi: framebuffer-hdmi {

		compatible = "amlogic,simple-framebuffer",

			     "simple-framebuffer";

		amlogic,pipeline = "vpu-hdmi";

		clocks = <&clkc CLKID_HDMI_PCLK>,

			 <&clkc CLKID_CLK81>,

			 <&clkc CLKID_GCLK_VENCI_INT0>;

		power-domains = <&pwrc_vpu>;

	};

};