dt-bindings: input: Add documentation for IBM Operation Panel

Document the bindings for the IBM Operation Panel, which provides
a simple interface to control a server. It has a display and three
buttons.
Also update MAINTAINERS for the new file.

Signed-off-by: Eddie James <[e-mail]>
Reviewed-by: Rob Herring <[e-mail]>
Acked-by: Joel Stanley <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Dmitry Torokhov <[e-mail]>

Documentation/devicetree/bindings/input/ibm,op-panel.yaml

···
+# SPDX-License-Identifier: (GPL-2.0 OR BSD-2-Clause)
+%YAML 1.2
+---
+$id: http://devicetree.org/schemas/input/ibm,op-panel.yaml#
+$schema: http://devicetree.org/meta-schemas/core.yaml#
+
+title: IBM Operation Panel
+
+maintainers:
+  - Eddie James <[e-mail]>
+
+allOf:
+  - $ref: input.yaml#
+
+description: |
+  The IBM Operation Panel provides a simple interface to control the connected
+  server. It has a display and three buttons: two directional arrows and one
+  'Enter' button.
+
+properties:
+  compatible:
+    const: ibm,op-panel
+
+  reg:
+    maxItems: 1
+
+  linux,keycodes:
+    minItems: 1
+    maxItems: 3
+
+required:
+  - compatible
+  - reg
+
+additionalProperties: false
+
+examples:
+  - |
+    #include <dt-bindings/i2c/i2c.h>
+    #include <dt-bindings/input/input.h>
+    i2c {
+        #address-cells = <1>;
+        #size-cells = <0>;
+
+        ibm-op-panel@62 {
+            compatible = "ibm,op-panel";
+            reg = <(0x62 | I2C_OWN_SLAVE_ADDRESS)>;
+            linux,keycodes = <KEY_UP>, <KEY_DOWN>, <KEY_ENTER>;
+        };
+    };

MAINTAINERS

···
 F:	Documentation/ia64/
 F:	arch/ia64/
 
+IBM Operation Panel Input Driver
+M:	Eddie James <[e-mail]>
+L:	[e-mail]
+S:	Maintained
+F:	Documentation/devicetree/bindings/input/ibm,op-panel.yaml
+
 IBM Power 842 compression accelerator
 M:	Haren Myneni <[e-mail]>
 S:	Supported