dt-bindings: mailbox: Add Apple mailbox bindings

# SPDX-License-Identifier: GPL-2.0 OR BSD-2-Clause

%YAML 1.2

---

$id: http://devicetree.org/schemas/mailbox/apple,mailbox.yaml#

$schema: http://devicetree.org/meta-schemas/core.yaml#

title: Apple Mailbox Controller

maintainers:

  - Hector Martin <marcan@marcan.st>

  - Sven Peter <sven@svenpeter.dev>

description:

  The Apple mailbox consists of two FIFOs used to exchange 64+32 bit

  messages between the main CPU and a co-processor. Multiple instances

  of this mailbox can be found on Apple SoCs.

  One of the two FIFOs is used to send data to a co-processor while the other

  FIFO is used for the other direction.

  Various clients implement different IPC protocols based on these simple

  messages and shared memory buffers.

properties:

  compatible:

    oneOf:

      - description:

          ASC mailboxes are the most common variant found on the M1 used

          for example for the display controller, the system management

          controller and the NVMe coprocessor.

        items:

          - const: apple,t8103-asc-mailbox

      - description:

          M3 mailboxes are an older variant with a slightly different MMIO

          interface still found on the M1. It is used for the Thunderbolt

          co-processors.

        items:

          - const: apple,t8103-m3-mailbox

  reg:

    maxItems: 1

  interrupts:

    items:

      - description: send fifo is empty interrupt

      - description: send fifo is not empty interrupt

      - description: receive fifo is empty interrupt

      - description: receive fifo is not empty interrupt

  interrupt-names:

    items:

      - const: send-empty

      - const: send-not-empty

      - const: recv-empty

      - const: recv-not-empty

  "#mbox-cells":

    const: 0

required:

  - compatible

  - reg

  - interrupts

  - interrupt-names

  - "#mbox-cells"

additionalProperties: false

examples:

  - |

        mailbox@77408000 {

                compatible = "apple,t8103-asc-mailbox";

                reg = <0x77408000 0x4000>;

                interrupts = <1 583 4>, <1 584 4>, <1 585 4>, <1 586 4>;

                interrupt-names = "send-empty", "send-not-empty",

                 "recv-empty", "recv-not-empty";

                #mbox-cells = <0>;

        };