dt-bindings: firmware: add google,gs101-acpm-ipc

Add bindings for the Samsung Exynos ACPM mailbox protocol.

Signed-off-by: Tudor Ambarus <tudor.ambarus@linaro.org>
Reviewed-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Link: https://lore.kernel.org/r/20250213-gs101-acpm-v9-1-8b0281b93c8b@linaro.org
Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>

Documentation/devicetree/bindings/firmware/google,gs101-acpm-ipc.yaml

@@ -0,0 +1,50 @@
+# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
+# Copyright 2024 Linaro Ltd.
+%YAML 1.2
+---
+$id: http://devicetree.org/schemas/firmware/google,gs101-acpm-ipc.yaml#
+$schema: http://devicetree.org/meta-schemas/core.yaml#
+
+title: Samsung Exynos ACPM mailbox protocol
+
+maintainers:
+  - Tudor Ambarus <tudor.ambarus@linaro.org>
+
+description: |
+  ACPM (Alive Clock and Power Manager) is a firmware that operates on the
+  APM (Active Power Management) module that handles overall power management
+  activities. ACPM and masters regard each other as independent hardware
+  component and communicate with each other using mailbox messages and
+  shared memory.
+
+  This binding is intended to define the interface the firmware implementing
+  ACPM provides for OSPM in the device tree.
+
+properties:
+  compatible:
+    const: google,gs101-acpm-ipc
+
+  mboxes:
+    maxItems: 1
+
+  shmem:
+    description:
+      List of phandle pointing to the shared memory (SHM) area. The memory
+      contains channels configuration data and the TX/RX ring buffers that
+      are used for passing messages to/from the ACPM firmware.
+    maxItems: 1
+
+required:
+  - compatible
+  - mboxes
+  - shmem
+
+additionalProperties: false
+
+examples:
+  - |
+    power-management {
+        compatible = "google,gs101-acpm-ipc";
+        mboxes = <&ap2apm_mailbox>;
+        shmem = <&apm_sram>;
+    };