dt-bindings: Document BCM283x CSI2/CCP2 receiver

Document the DT bindings for the CSI2/CCP2 receiver peripheral
(known as Unicam) on BCM283x SoCs.

Signed-off-by: Dave Stevenson <dave.stevenson@raspberrypi.org>
Acked-by: Rob Herring <robh@kernel.org>

Documentation/devicetree/bindings/media/bcm2835-unicam.txt

@@ -0,0 +1,85 @@
+Broadcom BCM283x Camera Interface (Unicam)
+------------------------------------------
+
+The Unicam block on BCM283x SoCs is the receiver for either
+CSI-2 or CCP2 data from image sensors or similar devices.
+
+The main platform using this SoC is the Raspberry Pi family of boards.
+On the Pi the VideoCore firmware can also control this hardware block,
+and driving it from two different processors will cause issues.
+To avoid this, the firmware checks the device tree configuration
+during boot. If it finds device tree nodes called csi0 or csi1 then
+it will stop the firmware accessing the block, and it can then
+safely be used via the device tree binding.
+
+Required properties:
+===================
+- compatible	: must be "brcm,bcm2835-unicam".
+- reg		: physical base address and length of the register sets for the
+		  device.
+- interrupts	: should contain the IRQ line for this Unicam instance.
+- clocks	: list of clock specifiers, corresponding to entries in
+		  clock-names property.
+- clock-names	: must contain an "lp" entry, matching entries in the
+		  clocks property.
+
+Unicam supports a single port node. It should contain one 'port' child node
+with child 'endpoint' node. Please refer to the bindings defined in
+Documentation/devicetree/bindings/media/video-interfaces.txt.
+
+Within the endpoint node the "remote-endpoint" and "data-lanes" properties
+are mandatory.
+Data lane reordering is not supported so the data lanes must be in order,
+starting at 1. The number of data lanes should represent the number of
+usable lanes for the hardware block. That may be limited by either the SoC or
+how the platform presents the interface, and the lower value must be used.
+
+Lane reordering is not supported on the clock lane either, so the optional
+property "clock-lane" will implicitly be <0>.
+Similarly lane inversion is not supported, therefore "lane-polarities" will
+implicitly be <0 0 0 0 0>.
+Neither of these values will be checked.
+
+Example:
+	csi1: csi1@7e801000 {
+		compatible = "brcm,bcm2835-unicam";
+		reg = <0x7e801000 0x800>,
+		      <0x7e802004 0x4>;
+		interrupts = <2 7>;
+		clocks = <&clocks BCM2835_CLOCK_CAM1>;
+		clock-names = "lp";
+
+		port {
+			csi1_ep: endpoint {
+				remote-endpoint = <&tc358743_0>;
+				data-lanes = <1 2>;
+			};
+		};
+	};
+
+	i2c0: i2c@7e205000 {
+		tc358743: csi-hdmi-bridge@0f {
+			compatible = "toshiba,tc358743";
+			reg = <0x0f>;
+
+			clocks = <&tc358743_clk>;
+			clock-names = "refclk";
+
+			tc358743_clk: bridge-clk {
+				compatible = "fixed-clock";
+				#clock-cells = <0>;
+				clock-frequency = <27000000>;
+			};
+
+			port {
+				tc358743_0: endpoint {
+					remote-endpoint = <&csi1_ep>;
+					clock-lanes = <0>;
+					data-lanes = <1 2>;
+					clock-noncontinuous;
+					link-frequencies =
+						/bits/ 64 <297000000>;
+				};
+			};
+		};
+	};