Device-Tree bindings for hisilicon ADE display controller driver

ADE (Advanced Display Engine) is the display controller which grab image
data from memory, do composition, do post image processing, generate RGB
timing stream and transfer to DSI.

Required properties:
- compatible: value should be "hisilicon,hi6220-ade".
- reg: physical base address and length of the ADE controller's registers.
- hisilicon,noc-syscon: ADE NOC QoS syscon.
- resets: The ADE reset controller node.
- interrupt: the ldi vblank interrupt number used.
- clocks: a list of phandle + clock-specifier pairs, one for each entry
  in clock-names.
- clock-names: should contain:
  "clk_ade_core" for the ADE core clock.
  "clk_codec_jpeg" for the media NOC QoS clock, which use the same clock with
  jpeg codec.
  "clk_ade_pix" for the ADE pixel clok.
- assigned-clocks: Should contain "clk_ade_core" and "clk_codec_jpeg" clocks'
  phandle + clock-specifier pairs.
- assigned-clock-rates: clock rates, one for each entry in assigned-clocks.
  The rate of "clk_ade_core" could be "360000000" or "180000000";
  The rate of "clk_codec_jpeg" could be or less than "1440000000".
  These rate values could be configured according to performance and power
  consumption.
- port: the output port. This contains one endpoint subnode, with its
  remote-endpoint set to the phandle of the connected DSI input endpoint.
  See Documentation/devicetree/bindings/graph.txt for more device graph info.

Optional properties:
- dma-coherent: Present if dma operations are coherent.


A example of HiKey board hi6220 SoC specific DT entry:
Example:

	ade: ade@f4100000 {
		compatible = "hisilicon,hi6220-ade";
		reg = <0x0 0xf4100000 0x0 0x7800>;
		reg-names = "ade_base";
		hisilicon,noc-syscon = <&medianoc_ade>;
		resets = <&media_ctrl MEDIA_ADE>;
		interrupts = <0 115 4>; /* ldi interrupt */

		clocks = <&media_ctrl HI6220_ADE_CORE>,
			 <&media_ctrl HI6220_CODEC_JPEG>,
			 <&media_ctrl HI6220_ADE_PIX_SRC>;
		/*clock name*/
		clock-names  = "clk_ade_core",
			       "clk_codec_jpeg",
			       "clk_ade_pix";

		assigned-clocks = <&media_ctrl HI6220_ADE_CORE>,
			<&media_ctrl HI6220_CODEC_JPEG>;
		assigned-clock-rates = <360000000>, <288000000>;
		dma-coherent;

		port {
			ade_out: endpoint {
				remote-endpoint = <&dsi_in>;
			};
		};
	};