dt-bindings: input: apple: Add Dockchannel HID bindings

This adds device tree bindings for the DockChannel HID node
required to enable internal keyboard/trackpad support on
Apple Silicon M2 and later laptops.

Signed-off-by: Michael Reeves <[email protected]>

Author: IntegralPilot

Documentation/devicetree/bindings/input/apple,dockchannel-hid.yaml

@@ -0,0 +1,93 @@
+# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
+%YAML 1.2
+---
+$id: http://devicetree.org/schemas/input/apple,dockchannel-hid.yaml#
+$schema: http://devicetree.org/meta-schemas/core.yaml#
+
+title: Apple DockChannel HID Transport
+
+maintainers:
+  - Michael Reeves <[email protected]>
+
+description: |
+  Transport layer for HID devices (keyboard, trackpad) connected via the
+  DockChannel FIFO interface on Apple Silicon SoCs.
+
+properties:
+  compatible:
+    oneOf:
+      - items:
+          - const: apple,t6020-dockchannel-hid
+      - items:
+          - const: apple,t8112-dockchannel-hid
+          - const: apple,t6020-dockchannel-hid
+
+  reg:
+    items:
+      - description: Configuration registers
+      - description: Data FIFO registers
+
+  reg-names:
+    items:
+      - const: config
+      - const: data
+
+  interrupts:
+    items:
+      - description: TX interrupt
+      - description: RX interrupt
+
+  interrupt-names:
+    items:
+      - const: tx
+      - const: rx
+
+  mboxes:
+    maxItems: 1
+
+  iommus:
+    maxItems: 1
+
+  apple,mtp:
+    $ref: /schemas/types.yaml#/definitions/phandle
+    description: Phandle to the co-processor (MTP) node.
+
+  keyboard:
+    type: object
+    description: |
+      Optional properties for the internal keyboard.
+    properties:
+      hid-country-code:
+        $ref: /schemas/types.yaml#/definitions/uint32
+        description: The USB HID country code for the keyboard layout.
+    additionalProperties: false
+
+required:
+  - compatible
+  - reg
+  - reg-names
+  - interrupts
+  - interrupt-names
+  - mboxes
+  - iommus
+  - apple,mtp
+
+additionalProperties: false
+
+examples:
+  - |
+    #include <dt-bindings/interrupt-controller/irq.h>
+    input@8000 {
+        compatible = "apple,t6020-dockchannel-hid";
+        reg = <0x8000 0x4000>, <0xc000 0x4000>;
+        reg-names = "config", "data";
+        mboxes = <&mtp_mbox>;
+        iommus = <&mtp_dart 1>;
+        apple,mtp = <&mtp>;
+        interrupts = <2 IRQ_TYPE_LEVEL_HIGH>, <3 IRQ_TYPE_LEVEL_HIGH>;
+        interrupt-names = "tx", "rx";
+
+        keyboard {
+            hid-country-code = <0>;
+        };
+    };