dt-bindings: remoteproc: add bindings for stm32 remote processor driver

STMicroelectronics STM32 Remoteproc

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

This document defines the binding for the remoteproc component that loads and

boots firmwares on the ST32MP family chipset.

Required properties:

- compatible:	Must be "st,stm32mp1-m4"

- reg:		Address ranges of the RETRAM and MCU SRAM memories used by the

		remote processor.

- resets:	Reference to a reset controller asserting the remote processor.

- st,syscfg-holdboot: Reference to the system configuration which holds the

		remote processor reset hold boot

	1st cell: phandle of syscon block

	2nd cell: register offset containing the hold boot setting

	3rd cell: register bitmask for the hold boot field

- st,syscfg-tz: Reference to the system configuration which holds the RCC trust

		zone mode

	1st cell: phandle to syscon block

	2nd cell: register offset containing the RCC trust zone mode setting

	3rd cell: register bitmask for the RCC trust zone mode bit

Optional properties:

- interrupts:	Should contain the watchdog interrupt

- mboxes:	This property is required only if the rpmsg/virtio functionality

		is used. List of phandle and mailbox channel specifiers:

		- a channel (a) used to communicate through virtqueues with the

		  remote proc.

		  Bi-directional channel:

		      - from local to remote = send message

		      - from remote to local = send message ack

		- a channel (b) working the opposite direction of channel (a)

		- a channel (c) used by the local proc to notify the remote proc

		  that it is about to be shut down.

		  Unidirectional channel:

		      - from local to remote, where ACK from the remote means

		        that it is ready for shutdown

- mbox-names:	This property is required if the mboxes property is used.

		- must be "vq0" for channel (a)

		- must be "vq1" for channel (b)

		- must be "shutdown" for channel (c)

- memory-region: List of phandles to the reserved memory regions associated with

		the remoteproc device. This is variable and describes the

		memories shared with the remote processor (eg: remoteproc

		firmware and carveouts, rpmsg vrings, ...).

		(see ../reserved-memory/reserved-memory.txt)

- st,syscfg-pdds: Reference to the system configuration which holds the remote

		processor deep sleep setting

	1st cell: phandle to syscon block

	2nd cell: register offset containing the deep sleep setting

	3rd cell: register bitmask for the deep sleep bit

- st,auto-boot:	If defined, when remoteproc is probed, it loads the default

		firmware and starts the remote processor.

Example:

	m4_rproc: m4@10000000 {

		compatible = "st,stm32mp1-m4";

		reg = <0x10000000 0x40000>,

		      <0x30000000 0x40000>,

		      <0x38000000 0x10000>;

		resets = <&rcc MCU_R>;

		st,syscfg-holdboot = <&rcc 0x10C 0x1>;

		st,syscfg-tz = <&rcc 0x000 0x1>;

	};