Device-Tree bindings for Samsung Exynos Embedded DisplayPort Transmitter(eDP)

DisplayPort is industry standard to accommodate the growing board adoption
of digital display technology within the PC and CE industries.
It consolidates the internal and external connection methods to reduce device
complexity and cost. It also supports necessary features for important cross
industry applications and provides performance scalability to enable the next
generation of displays that feature higher color depths, refresh rates, and
display resolutions.

eDP (embedded display port) device is compliant with Embedded DisplayPort
standard as follows,
- DisplayPort standard 1.1a for Exynos5250 and Exynos5260.
- DisplayPort standard 1.3 for Exynos5422s and Exynos5800.

eDP resides between FIMD and panel or FIMD and bridge such as LVDS.

The Exynos display port interface should be configured based on
the type of panel connected to it.

We use two nodes:
	-dp-controller node
	-dptx-phy node(defined inside dp-controller node)

For the DP-PHY initialization, we use the dptx-phy node.
Required properties for dptx-phy: deprecated, use phys and phy-names
	-reg: deprecated
		Base address of DP PHY register.
	-samsung,enable-mask: deprecated
		The bit-mask used to enable/disable DP PHY.

For the Panel initialization, we read data from dp-controller node.
Required properties for dp-controller:
	-compatible:
		should be "samsung,exynos5-dp".
	-reg:
		physical base address of the controller and length
		of memory mapped region.
	-interrupts:
		interrupt combiner values.
	-clocks:
		from common clock binding: handle to dp clock.
	-clock-names:
		from common clock binding: Shall be "dp".
	-interrupt-parent:
		phandle to Interrupt combiner node.
	-phys:
		from general PHY binding: the phandle for the PHY device.
	-phy-names:
		from general PHY binding: Should be "dp".
	-samsung,color-space:
		input video data format.
			COLOR_RGB = 0, COLOR_YCBCR422 = 1, COLOR_YCBCR444 = 2
	-samsung,dynamic-range:
		dynamic range for input video data.
			VESA = 0, CEA = 1
	-samsung,ycbcr-coeff:
		YCbCr co-efficients for input video.
			COLOR_YCBCR601 = 0, COLOR_YCBCR709 = 1
	-samsung,color-depth:
		number of bits per colour component.
			COLOR_6 = 0, COLOR_8 = 1, COLOR_10 = 2, COLOR_12 = 3
	-samsung,link-rate:
		link rate supported by the panel.
			LINK_RATE_1_62GBPS = 0x6, LINK_RATE_2_70GBPS = 0x0A
	-samsung,lane-count:
		number of lanes supported by the panel.
			LANE_COUNT1 = 1, LANE_COUNT2 = 2, LANE_COUNT4 = 4
	- display-timings: timings for the connected panel as described by
		Documentation/devicetree/bindings/display/display-timing.txt

Optional properties for dp-controller:
	-interlaced:
		interlace scan mode.
			Progressive if defined, Interlaced if not defined
	-vsync-active-high:
		VSYNC polarity configuration.
			High if defined, Low if not defined
	-hsync-active-high:
		HSYNC polarity configuration.
			High if defined, Low if not defined
	-samsung,hpd-gpio:
		Hotplug detect GPIO.
			Indicates which GPIO should be used for hotplug
			detection
Video interfaces:
  Device node can contain video interface port nodes according to [1].
  The following are properties specific to those nodes:

  endpoint node connected to bridge or panel node:
   - remote-endpoint: specifies the endpoint in panel or bridge node.
		      This node is required in all kinds of exynos dp
		      to represent the connection between dp and bridge
		      or dp and panel.

[1]: Documentation/devicetree/bindings/media/video-interfaces.txt

Example:

SOC specific portion:
	dp-controller {
		compatible = "samsung,exynos5-dp";
		reg = <0x145b0000 0x10000>;
		interrupts = <10 3>;
		interrupt-parent = <&combiner>;
		clocks = <&clock 342>;
		clock-names = "dp";

		phys = <&dp_phy>;
		phy-names = "dp";
	};

Board Specific portion:
	dp-controller {
		samsung,color-space = <0>;
		samsung,dynamic-range = <0>;
		samsung,ycbcr-coeff = <0>;
		samsung,color-depth = <1>;
		samsung,link-rate = <0x0a>;
		samsung,lane-count = <4>;

		display-timings {
			native-mode = <&lcd_timing>;
			lcd_timing: 1366x768 {
				clock-frequency = <70589280>;
				hactive = <1366>;
				vactive = <768>;
				hfront-porch = <40>;
				hback-porch = <40>;
				hsync-len = <32>;
				vback-porch = <10>;
				vfront-porch = <12>;
				vsync-len = <6>;
			};
		};

		ports {
			port {
				dp_out: endpoint {
					remote-endpoint = <&dp_in>;
				};
			};
		};

		panel {
			...
			port {
				dp_in: endpoint {
					remote-endpoint = <&dp_out>;
				};
			};
		};
	};