dt-bindings: mailbox: add google,gs101-mbox

Add bindings for the Samsung Exynos Mailbox Controller.

Signed-off-by: Tudor Ambarus <[e-mail]>
Reviewed-by: Krzysztof Kozlowski <[e-mail]>
Signed-off-by: Jassi Brar <[e-mail]>

Documentation/devicetree/bindings/mailbox/google,gs101-mbox.yaml

···
+# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
+# Copyright 2024 Linaro Ltd.
+%YAML 1.2
+---
+$id: http://devicetree.org/schemas/mailbox/google,gs101-mbox.yaml#
+$schema: http://devicetree.org/meta-schemas/core.yaml#
+
+title: Samsung Exynos Mailbox Controller
+
+maintainers:
+  - Tudor Ambarus <[e-mail]>
+
+description:
+  The Samsung Exynos mailbox controller, used on Google GS101 SoC, has 16 flag
+  bits for hardware interrupt generation and a shared register for passing
+  mailbox messages. When the controller is used by the ACPM interface
+  the shared register is ignored and the mailbox controller acts as a doorbell.
+  The controller just raises the interrupt to the firmware after the
+  ACPM interface has written the message to SRAM.
+
+properties:
+  compatible:
+    const: google,gs101-mbox
+
+  reg:
+    maxItems: 1
+
+  clocks:
+    maxItems: 1
+
+  clock-names:
+    items:
+      - const: pclk
+
+  interrupts:
+    description: IRQ line for the RX mailbox.
+    maxItems: 1
+
+  '#mbox-cells':
+    const: 0
+
+required:
+  - compatible
+  - reg
+  - clocks
+  - clock-names
+  - interrupts
+  - '#mbox-cells'
+
+additionalProperties: false
+
+examples:
+  - |
+    #include <dt-bindings/interrupt-controller/arm-gic.h>
+    #include <dt-bindings/clock/google,gs101.h>
+
+    soc {
+        #address-cells = <1>;
+        #size-cells = <1>;
+
+        ap2apm_mailbox: mailbox@17610000 {
+            compatible = "google,gs101-mbox";
+            reg = <0x17610000 0x1000>;
+            clocks = <&cmu_apm CLK_GOUT_APM_MAILBOX_APM_AP_PCLK>;
+            clock-names = "pclk";
+            interrupts = <GIC_SPI 73 IRQ_TYPE_LEVEL_HIGH 0>;
+            #mbox-cells = <0>;
+        };
+    };