ZTE VOU Display Controller

This is a display controller found on ZTE ZX296718 SoC.  It includes multiple
Graphic Layer (GL) and Video Layer (VL), two Mixers/Channels, and a few blocks
handling scaling, color space conversion etc.  VOU also integrates the support
for typical output devices, like HDMI, TV Encoder, VGA, and RGB LCD.

* Master VOU node

It must be the parent node of all the sub-device nodes.

Required properties:
 - compatible: should be "zte,zx296718-vou"
 - #address-cells: should be <1>
 - #size-cells: should be <1>
 - ranges: list of address translations between VOU and sub-devices

* VOU DPC device

Required properties:
 - compatible: should be "zte,zx296718-dpc"
 - reg: Physical base address and length of DPC register regions, one for each
   entry in 'reg-names'
 - reg-names: The names of register regions. The following regions are required:
	"osd"
	"timing_ctrl"
	"dtrc"
	"vou_ctrl"
	"otfppu"
 - interrupts: VOU DPC interrupt number to CPU
 - clocks: A list of phandle + clock-specifier pairs, one for each entry
   in 'clock-names'
 - clock-names: A list of clock names.  The following clocks are required:
	"aclk"
	"ppu_wclk"
	"main_wclk"
	"aux_wclk"

* HDMI output device

Required properties:
 - compatible: should be "zte,zx296718-hdmi"
 - reg: Physical base address and length of the HDMI device IO region
 - interrupts : HDMI interrupt number to CPU
 - clocks: A list of phandle + clock-specifier pairs, one for each entry
   in 'clock-names'
 - clock-names: A list of clock names.  The following clocks are required:
	"osc_cec"
	"osc_clk"
	"xclk"

Example:

vou: vou@1440000 {
	compatible = "zte,zx296718-vou";
	#address-cells = <1>;
	#size-cells = <1>;
	ranges = <0 0x1440000 0x10000>;

	dpc: dpc@0 {
		compatible = "zte,zx296718-dpc";
		reg = <0x0000 0x1000>, <0x1000 0x1000>,
		      <0x5000 0x1000>, <0x6000 0x1000>,
		      <0xa000 0x1000>;
		reg-names = "osd", "timing_ctrl",
			    "dtrc", "vou_ctrl",
			    "otfppu";
		interrupts = <GIC_SPI 81 IRQ_TYPE_LEVEL_HIGH>;
		clocks = <&topcrm VOU_ACLK>, <&topcrm VOU_PPU_WCLK>,
			 <&topcrm VOU_MAIN_WCLK>, <&topcrm VOU_AUX_WCLK>;
		clock-names = "aclk", "ppu_wclk",
			      "main_wclk", "aux_wclk";
	};

	hdmi: hdmi@c000 {
		compatible = "zte,zx296718-hdmi";
		reg = <0xc000 0x4000>;
		interrupts = <GIC_SPI 82 IRQ_TYPE_EDGE_RISING>;
		clocks = <&topcrm HDMI_OSC_CEC>,
			 <&topcrm HDMI_OSC_CLK>,
			 <&topcrm HDMI_XCLK>;
		clock-names = "osc_cec", "osc_clk", "xclk";
	};
};