media: dt-bindings: Document the Rockchip VPU bindings

device-tree bindings for rockchip VPU codec

Rockchip (Video Processing Unit) present in various Rockchip platforms,

such as RK3288 and RK3399.

Required properties:

- compatible: value should be one of the following

		"rockchip,rk3288-vpu";

		"rockchip,rk3399-vpu";

- interrupts: encoding and decoding interrupt specifiers

- interrupt-names: should be "vepu" and "vdpu"

- clocks: phandle to VPU aclk, hclk clocks

- clock-names: should be "aclk" and "hclk"

- power-domains: phandle to power domain node

- iommus: phandle to a iommu node

Example:

SoC-specific DT entry:

	vpu: video-codec@ff9a0000 {

		compatible = "rockchip,rk3288-vpu";

		reg = <0x0 0xff9a0000 0x0 0x800>;

		interrupts = <GIC_SPI 9 IRQ_TYPE_LEVEL_HIGH>,

			     <GIC_SPI 10 IRQ_TYPE_LEVEL_HIGH>;

		interrupt-names = "vepu", "vdpu";

		clocks = <&cru ACLK_VCODEC>, <&cru HCLK_VCODEC>;

		clock-names = "aclk", "hclk";

		power-domains = <&power RK3288_PD_VIDEO>;

		iommus = <&vpu_mmu>;

	};