dt-bindings: soc: apple: Add Dockchannel and MTP bindings

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

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

Author: IntegralPilot

Documentation/devicetree/bindings/soc/apple/apple,dockchannel.yaml

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+# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
+# Copyright (c) 2025 The Asahi Linux contributors
+%YAML 1.2
+---
+$id: http://devicetree.org/schemas/soc/apple/apple,dockchannel.yaml#
+$schema: http://devicetree.org/meta-schemas/core.yaml#
+
+title: Apple DockChannel FIFO
+
+maintainers:
+  - Michael Reeves <[email protected]>
+
+description: |
+  DockChannel is a hardware FIFO and interrupt controller used on Apple SoCs
+  for low-latency communication with co-processors.
+
+properties:
+  compatible:
+    oneOf:
+      - items:
+          - const: apple,t6020-dockchannel
+      - items:
+          - const: apple,t8112-dockchannel
+          - const: apple,t6020-dockchannel
+
+  reg:
+    maxItems: 1
+
+  interrupts:
+    maxItems: 1
+
+  interrupt-controller: true
+
+  "#interrupt-cells":
+    const: 2
+
+  ranges: true
+
+  nonposted-mmio: true
+
+  "#address-cells":
+    const: 1
+
+  "#size-cells":
+    const: 1
+
+patternProperties:
+  "^input@[0-9a-f]+$":
+    $ref: /schemas/input/apple,dockchannel-hid.yaml
+
+required:
+  - compatible
+  - reg
+  - interrupts
+  - interrupt-controller
+  - "#interrupt-cells"
+  - ranges
+  - "#address-cells"
+  - "#size-cells"
+
+additionalProperties: false
+
+examples:
+  - |
+    #include <dt-bindings/interrupt-controller/apple-aic.h>
+    #include <dt-bindings/interrupt-controller/irq.h>
+
+    soc {
+        #address-cells = <2>;
+        #size-cells = <2>;
+
+        fifo@2a9b14000 {
+            compatible = "apple,t6020-dockchannel";
+            reg = <0x2 0xa9b14000 0x0 0x4000>;
+            interrupt-parent = <&aic>;
+            interrupts = <AIC_IRQ 677 IRQ_TYPE_LEVEL_HIGH>;
+            ranges = <0 0x2 0xa9b28000 0x20000>;
+            nonposted-mmio;
+            #address-cells = <1>;
+            #size-cells = <1>;
+            interrupt-controller;
+            #interrupt-cells = <2>;
+        };
+    };

Documentation/devicetree/bindings/soc/apple/apple,mtp.yaml

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+# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
+%YAML 1.2
+---
+$id: http://devicetree.org/schemas/soc/apple/apple,mtp.yaml#
+$schema: http://devicetree.org/meta-schemas/core.yaml#
+
+title: Apple MTP Co-processor
+
+maintainers:
+  - Michael Reeves <[email protected]>
+
+description: |
+  The MTP (Multi-Touch Processor) is an ARM-based co-processor
+  responsible for assisting with DockChannel HID communication on
+  M2 and later Apple Silicon laptops.
+
+properties:
+  compatible:
+    oneOf:
+      - items:
+          - const: apple,t6020-mtp
+      - items:
+          - const: apple,t8112-mtp
+          - const: apple,t6020-mtp
+
+  reg:
+    items:
+      - description: ASC control registers
+      - description: SRAM/Shared memory region
+
+  reg-names:
+    items:
+      - const: asc
+      - const: sram
+
+required:
+  - compatible
+  - reg
+  - reg-names
+
+additionalProperties: false
+
+examples:
+  - |
+    soc {
+        #address-cells = <2>;
+        #size-cells = <2>;
+
+        mtp: mtp@2a9400000 {
+            compatible = "apple,t6020-mtp";
+            reg = <0x2 0xa9400000 0x0 0x4000>,
+                  <0x2 0xa9c00000 0x0 0x100000>;
+            reg-names = "asc", "sram";
+        };
+    };