dt-bindings: input: Add Cypress TT21000 touchscreen controller

Add the Cypress TrueTouch Generation 5 touchscreen device tree bindings
documentation. It can use I2C or SPI bus.
This touchscreen can handle some defined zone that are designed and
sent as button. To be able to customize the keycode sent, the
"linux,code" property in a "button" sub-node can be used.
Signed-off-by: Alistair Francis <alistair@alistair23.me>
Reviewed-by: Linus Walleij <linus.walleij@linaro.org>
Reviewed-by: Rob Herring <robh@kernel.org>
Link: https://lore.kernel.org/r/20221026114908.191472-3-alistair@alistair23.meSigned-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>

Documentation/devicetree/bindings/input/touchscreen/cypress,tt21000.yaml

+# SPDX-License-Identifier: GPL-2.0-only OR BSD-2-Clause
+%YAML 1.2
+---
+$id: http://devicetree.org/schemas/input/touchscreen/cypress,tt21000.yaml#
+$schema: http://devicetree.org/meta-schemas/core.yaml#
+
+title: Cypress TT21000 touchscreen controller
+
+description: The Cypress TT21000 series (also known as "CYTTSP5" after
+  the marketing name Cypress TrueTouch Standard Product series 5).
+
+maintainers:
+  - Alistair Francis <alistair@alistair23.me>
+
+allOf:
+  - $ref: touchscreen.yaml#
+
+properties:
+  compatible:
+    const: cypress,tt21000
+
+  reg:
+    maxItems: 1
+
+  '#address-cells':
+    const: 1
+
+  '#size-cells':
+    const: 0
+
+  interrupts:
+    maxItems: 1
+
+  vdd-supply:
+    description: Regulator for voltage.
+
+  reset-gpios:
+    maxItems: 1
+
+  linux,keycodes:
+    description: EV_ABS specific event code generated by the axis.
+
+patternProperties:
+  "^button@[0-9]+$":
+    type: object
+    $ref: ../input.yaml#
+    properties:
+      reg:
+        maxItems: 1
+      linux,keycodes:
+        description: Keycode to emit
+
+    required:
+      - reg
+      - linux,keycodes
+
+    additionalProperties: false
+
+required:
+  - compatible
+  - reg
+  - interrupts
+  - vdd-supply
+
+unevaluatedProperties: false
+
+examples:
+  - |
+    #include <dt-bindings/interrupt-controller/irq.h>
+    #include <dt-bindings/gpio/gpio.h>
+    #include <dt-bindings/input/linux-event-codes.h>
+
+    i2c {
+        #address-cells = <1>;
+        #size-cells = <0>;
+
+        touchscreen@24 {
+            #address-cells = <1>;
+            #size-cells = <0>;
+
+            compatible = "cypress,tt21000";
+            reg = <0x24>;
+            pinctrl-names = "default";
+            pinctrl-0 = <&tp_reset_ds203>;
+            interrupt-parent = <&pio>;
+            interrupts = <1 5 IRQ_TYPE_LEVEL_LOW>;
+            reset-gpios = <&pio 7 1 GPIO_ACTIVE_LOW>;
+            vdd-supply = <&reg_touch>;
+
+            button@0 {
+                reg = <0>;
+                linux,keycodes = <KEY_HOMEPAGE>;
+            };
+
+            button@1 {
+                reg = <1>;
+                linux,keycodes = <KEY_MENU>;
+            };
+
+            button@2 {
+                reg = <2>;
+                linux,keycodes = <KEY_BACK>;
+            };
+        };
+    };
+...