Broadcom VC4 (VideoCore4) GPU

The VC4 device present on the Raspberry Pi includes a display system
with HDMI output and the HVS (Hardware Video Scaler) for compositing
display planes.

Required properties for VC4:
- compatible:	Should be "brcm,bcm2835-vc4"

Required properties for Pixel Valve:
- compatible:	Should be one of "brcm,bcm2835-pixelvalve0",
		  "brcm,bcm2835-pixelvalve1", or "brcm,bcm2835-pixelvalve2"
- reg:		Physical base address and length of the PV's registers
- interrupts:	The interrupt number
		  See bindings/interrupt-controller/brcm,bcm2835-armctrl-ic.txt

Required properties for HVS:
- compatible:	Should be "brcm,bcm2835-hvs"
- reg:		Physical base address and length of the HVS's registers
- interrupts:	The interrupt number
		  See bindings/interrupt-controller/brcm,bcm2835-armctrl-ic.txt

Required properties for HDMI
- compatible:	Should be "brcm,bcm2835-hdmi"
- reg:		Physical base address and length of the two register ranges
		  ("HDMI" and "HD", in that order)
- interrupts:	The interrupt numbers
		  See bindings/interrupt-controller/brcm,bcm2835-armctrl-ic.txt
- ddc:		phandle of the I2C controller used for DDC EDID probing
- clocks:	a) hdmi: The HDMI state machine clock
		b) pixel: The pixel clock.

Optional properties for HDMI:
- hpd-gpios:	The GPIO pin for HDMI hotplug detect (if it doesn't appear
		  as an interrupt/status bit in the HDMI controller
		  itself).  See bindings/pinctrl/brcm,bcm2835-gpio.txt

Example:
pixelvalve@7e807000 {
	compatible = "brcm,bcm2835-pixelvalve2";
	reg = <0x7e807000 0x100>;
	interrupts = <2 10>; /* pixelvalve */
};

hvs@7e400000 {
	compatible = "brcm,bcm2835-hvs";
	reg = <0x7e400000 0x6000>;
	interrupts = <2 1>;
};

hdmi: hdmi@7e902000 {
	compatible = "brcm,bcm2835-hdmi";
	reg = <0x7e902000 0x600>,
	      <0x7e808000 0x100>;
	interrupts = <2 8>, <2 9>;
	ddc = <&i2c2>;
	hpd-gpios = <&gpio 46 GPIO_ACTIVE_HIGH>;
	clocks = <&clocks BCM2835_PLLH_PIX>,
		 <&clocks BCM2835_CLOCK_HSM>;
	clock-names = "pixel", "hdmi";
};

vc4: gpu {
	compatible = "brcm,bcm2835-vc4";
};