Documentation: dt: mailbox: Add TI Message Manager

Texas Instruments' Message Manager Driver

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

The Texas Instruments' Message Manager is a mailbox controller that has

configurable queues selectable at SoC(System on Chip) integration. The Message

manager is broken up into queues in different address regions that are called

"proxies" - each instance is unidirectional and is instantiated at SoC

integration level to indicate receive or transmit path.

Message Manager Device Node:

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

Required properties:

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

- compatible:		Shall be: "ti,k2g-message-manager"

- reg-names 		queue_proxy_region - Map the queue proxy region.

			queue_state_debug_region - Map the queue state debug

			region.

- reg:			Contains the register map per reg-names.

- #mbox-cells		Shall be 2. Contains the queue ID and proxy ID in that

		        order referring to the transfer path.

- interrupt-names:	Contains interrupt names matching the rx transfer path

			for a given SoC. Receive interrupts shall be of the

			format: "rx_<QID>_<PID>".

			For ti,k2g-message-manager, this shall contain:

				"rx_005_002", "rx_057_002"

- interrupts:		Contains the interrupt information corresponding to

			interrupt-names property.

Example(K2G):

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

	msgmgr: msgmgr@02a00000 {

		compatible = "ti,k2g-message-manager";

		#mbox-cells = <2>;

		reg-names = "queue_proxy_region", "queue_state_debug_region";

		reg = <0x02a00000 0x400000>, <0x028c3400 0x400>;

		interrupt-names = "rx_005", "rx_057";

		interrupts = <GIC_SPI 324 IRQ_TYPE_LEVEL_HIGH>,

			     <GIC_SPI 327 IRQ_TYPE_LEVEL_HIGH>;

	};

	pmmc: pmmc {

		[...]

		mbox-names = "rx", "tx";

		# RX queue ID is 5, proxy ID is 2

		# TX queue ID is 0, proxy ID is 0

		mboxes= <&msgmgr 5 2>,

			<&msgmgr 0 0>;

		[...]

	};