dt-bindings: input: Convert adc-keys to DT schema

Convert the adc-keys binding to DT schema format.

The old binding has 'label' as required, but it should never be
required given it's just a human readable description.

Signed-off-by: Rob Herring <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Dmitry Torokhov <[e-mail]>

Documentation/devicetree/bindings/input/adc-keys.txt

···
-ADC attached resistor ladder buttons
-------------------------------------
-
-Required properties:
- - compatible: "adc-keys"
- - io-channels: Phandle to an ADC channel
- - io-channel-names = "buttons";
- - keyup-threshold-microvolt: Voltage above or equal to which all the keys are
-			      considered up.
-
-Optional properties:
-	- poll-interval: Poll interval time in milliseconds
-	- autorepeat: Boolean, Enable auto repeat feature of Linux input
-	  subsystem.
-
-Each button (key) is represented as a sub-node of "adc-keys":
-
-Required subnode-properties:
-	- label: Descriptive name of the key.
-	- linux,code: Keycode to emit.
-	- press-threshold-microvolt: voltage above or equal to which this key is
-				     considered pressed.
-
-No two values of press-threshold-microvolt may be the same.
-All values of press-threshold-microvolt must be less than
-keyup-threshold-microvolt.
-
-Example:
-
-#include <dt-bindings/input/input.h>
-
-	adc-keys {
-		compatible = "adc-keys";
-		io-channels = <&lradc 0>;
-		io-channel-names = "buttons";
-		keyup-threshold-microvolt = <2000000>;
-
-		button-up {
-			label = "Volume Up";
-			linux,code = <KEY_VOLUMEUP>;
-			press-threshold-microvolt = <1500000>;
-		};
-
-		button-down {
-			label = "Volume Down";
-			linux,code = <KEY_VOLUMEDOWN>;
-			press-threshold-microvolt = <1000000>;
-		};
-
-		button-enter {
-			label = "Enter";
-			linux,code = <KEY_ENTER>;
-			press-threshold-microvolt = <500000>;
-		};
-	};
-
-+--------------------------------+------------------------+
-| 2.000.000 <= value             | no key pressed         |
-+--------------------------------+------------------------+
-| 1.500.000 <= value < 2.000.000 | KEY_VOLUMEUP pressed   |
-+--------------------------------+------------------------+
-| 1.000.000 <= value < 1.500.000 | KEY_VOLUMEDOWN pressed |
-+--------------------------------+------------------------+
-|   500.000 <= value < 1.000.000 | KEY_ENTER pressed      |
-+--------------------------------+------------------------+
-|              value <   500.000 | no key pressed         |
-+--------------------------------+------------------------+

Documentation/devicetree/bindings/input/adc-keys.yaml

···
+# SPDX-License-Identifier: GPL-2.0
+%YAML 1.2
+---
+$id: http://devicetree.org/schemas/input/adc-keys.yaml#
+$schema: http://devicetree.org/meta-schemas/core.yaml#
+
+title: ADC attached resistor ladder buttons
+
+maintainers:
+  - Alexandre Belloni <[e-mail]>
+
+allOf:
+  - $ref: input.yaml#
+
+properties:
+  compatible:
+    const: adc-keys
+
+  io-channels:
+    maxItems: 1
+
+  io-channel-names:
+    const: buttons
+
+  keyup-threshold-microvolt:
+    description:
+      Voltage above or equal to which all the keys are considered up.
+
+  poll-interval: true
+  autorepeat: true
+
+patternProperties:
+  '^button-':
+    type: object
+    $ref: input.yaml#
+    additionalProperties: false
+    description:
+      Each button (key) is represented as a sub-node.
+
+    properties:
+      label: true
+
+      linux,code: true
+
+      press-threshold-microvolt:
+        description:
+          Voltage above or equal to which this key is considered pressed. No
+          two values of press-threshold-microvolt may be the same. All values
+          of press-threshold-microvolt must be less than
+          keyup-threshold-microvolt.
+
+    required:
+      - linux,code
+      - press-threshold-microvolt
+
+required:
+  - compatible
+  - io-channels
+  - io-channel-names
+  - keyup-threshold-microvolt
+
+additionalProperties: false
+
+examples:
+  - |
+    #include <dt-bindings/input/input.h>
+    // +--------------------------------+------------------------+
+    // | 2.000.000 <= value             | no key pressed         |
+    // +--------------------------------+------------------------+
+    // | 1.500.000 <= value < 2.000.000 | KEY_VOLUMEUP pressed   |
+    // +--------------------------------+------------------------+
+    // | 1.000.000 <= value < 1.500.000 | KEY_VOLUMEDOWN pressed |
+    // +--------------------------------+------------------------+
+    // |   500.000 <= value < 1.000.000 | KEY_ENTER pressed      |
+    // +--------------------------------+------------------------+
+    // |              value <   500.000 | no key pressed         |
+    // +--------------------------------+------------------------+
+
+    adc-keys {
+        compatible = "adc-keys";
+        io-channels = <&lradc 0>;
+        io-channel-names = "buttons";
+        keyup-threshold-microvolt = <2000000>;
+
+        button-up {
+            label = "Volume Up";
+            linux,code = <KEY_VOLUMEUP>;
+            press-threshold-microvolt = <1500000>;
+        };
+
+        button-down {
+            label = "Volume Down";
+            linux,code = <KEY_VOLUMEDOWN>;
+            press-threshold-microvolt = <1000000>;
+        };
+
+        button-enter {
+            label = "Enter";
+            linux,code = <KEY_ENTER>;
+            press-threshold-microvolt = <500000>;
+        };
+    };
+...