dt-bindings: input: Add bindings for Mediatek matrix keypad

This patch add devicetree bindings for Mediatek matrix keypad driver.
Signed-off-by: fengping.yu <fengping.yu@mediatek.com>
Reviewed-by: Marco Felsch <m.felsch@pengutronix.de>
Signed-off-by: Mattijs Korpershoek <mkorpershoek@baylibre.com>
Reviewed-by: Rob Herring <robh@kernel.org>
Reviewed-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@collabora.com>
Link: https://lore.kernel.org/r/20220303154302.252041-2-mkorpershoek@baylibre.comSigned-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>

Documentation/devicetree/bindings/input/mediatek,mt6779-keypad.yaml

+# SPDX-License-Identifier: (GPL-2.0 OR BSD-2-Clause)
+%YAML 1.2
+---
+$id: http://devicetree.org/schemas/input/mediatek,mt6779-keypad.yaml#
+$schema: http://devicetree.org/meta-schemas/core.yaml#
+
+title: Mediatek's Keypad Controller device tree bindings
+
+maintainers:
+  - Fengping Yu <fengping.yu@mediatek.com>
+
+allOf:
+  - $ref: "/schemas/input/matrix-keymap.yaml#"
+
+description: |
+  Mediatek's Keypad controller is used to interface a SoC with a matrix-type
+  keypad device. The keypad controller supports multiple row and column lines.
+  A key can be placed at each intersection of a unique row and a unique column.
+  The keypad controller can sense a key-press and key-release and report the
+  event using a interrupt to the cpu.
+
+properties:
+  compatible:
+    oneOf:
+      - const: mediatek,mt6779-keypad
+      - items:
+          - enum:
+              - mediatek,mt6873-keypad
+          - const: mediatek,mt6779-keypad
+
+  reg:
+    maxItems: 1
+
+  interrupts:
+    maxItems: 1
+
+  clocks:
+    maxItems: 1
+
+  clock-names:
+    items:
+      - const: kpd
+
+  wakeup-source:
+    description: use any event on keypad as wakeup event
+    type: boolean
+
+  debounce-delay-ms:
+    maximum: 256
+    default: 16
+
+required:
+  - compatible
+  - reg
+  - interrupts
+  - clocks
+  - clock-names
+
+additionalProperties: false
+
+examples:
+  - |
+    #include <dt-bindings/input/input.h>
+    #include <dt-bindings/interrupt-controller/arm-gic.h>
+
+    soc {
+        #address-cells = <2>;
+        #size-cells = <2>;
+
+        keyboard@10010000 {
+          compatible = "mediatek,mt6779-keypad";
+          reg = <0 0x10010000 0 0x1000>;
+          interrupts = <GIC_SPI 75 IRQ_TYPE_EDGE_FALLING>;
+          clocks = <&clk26m>;
+          clock-names = "kpd";
+        };
+    };