of: Add MIPI DSI bus device tree bindings

MIPI DSI (Display Serial Interface) busses

==========================================

The MIPI Display Serial Interface specifies a serial bus and a protocol for

communication between a host and up to four peripherals. This document will

define the syntax used to represent a DSI bus in a device tree.

This document describes DSI bus-specific properties only or defines existing

standard properties in the context of the DSI bus.

Each DSI host provides a DSI bus. The DSI host controller's node contains a

set of properties that characterize the bus. Child nodes describe individual

peripherals on that bus.

The following assumes that only a single peripheral is connected to a DSI

host. Experience shows that this is true for the large majority of setups.

DSI host

--------

In addition to the standard properties and those defined by the parent bus of

a DSI host, the following properties apply to a node representing a DSI host.

Required properties:

- #address-cells: The number of cells required to represent an address on the

  bus. DSI peripherals are addressed using a 2-bit virtual channel number, so

  a maximum of 4 devices can be addressed on a single bus. Hence the value of

  this property should be 1.

- #size-cells: Should be 0. There are cases where it makes sense to use a

  different value here. See below.

DSI peripheral

--------------

Peripherals are represented as child nodes of the DSI host's node. Properties

described here apply to all DSI peripherals, but individual bindings may want

to define additional, device-specific properties.

Required properties:

- reg: The virtual channel number of a DSI peripheral. Must be in the range

  from 0 to 3.

Some DSI peripherals respond to more than a single virtual channel. In that

case two alternative representations can be chosen:

- The reg property can take multiple entries, one for each virtual channel

  that the peripheral responds to.

- If the virtual channels that a peripheral responds to are consecutive, the

  #size-cells can be set to 1. The first cell of each entry in the reg

  property is the number of the first virtual channel and the second cell is

  the number of consecutive virtual channels.

Example

-------

	dsi-host {

		...

		#address-cells = <1>;

		#size-cells = <0>;

		/* peripheral responds to virtual channel 0 */

		peripheral@0 {

			compatible = "...";

			reg = <0>;

		};

		...

	};

	dsi-host {

		...

		#address-cells = <1>;

		#size-cells = <0>;

		/* peripheral responds to virtual channels 0 and 2 */

		peripheral@0 {

			compatible = "...";

			reg = <0, 2>;

		};

		...

	};

	dsi-host {

		...

		#address-cells = <1>;

		#size-cells = <1>;

		/* peripheral responds to virtual channels 1, 2 and 3 */

		peripheral@1 {

			compatible = "...";

			reg = <1 3>;

		};

		...

	};