dt-bindings: counter: add interrupt-counter binding

Add binding for the interrupt counter node
Signed-off-by: Oleksij Rempel <o.rempel@pengutronix.de>
Reviewed-by: Linus Walleij <linus.walleij@linaro.org>
Acked-by: William Breathitt Gray <vilhelm.gray@gmail.com>
Reviewed-by: Rob Herring <robh@kernel.org>
Link: https://lore.kernel.org/r/20210301080401.22190-2-o.rempel@pengutronix.deSigned-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>

Documentation/devicetree/bindings/counter/interrupt-counter.yaml

+# SPDX-License-Identifier: GPL-2.0
+%YAML 1.2
+---
+$id: http://devicetree.org/schemas/counter/interrupt-counter.yaml#
+$schema: http://devicetree.org/meta-schemas/core.yaml#
+
+title: Interrupt counter
+
+maintainers:
+  - Oleksij Rempel <o.rempel@pengutronix.de>
+
+description: |
+  A generic interrupt counter to measure interrupt frequency. It was developed
+  and used for agricultural devices to measure rotation speed of wheels or
+  other tools. Since the direction of rotation is not important, only one
+  signal line is needed.
+  Interrupts or gpios are required. If both are defined, the interrupt will
+  take precedence for counting interrupts.
+
+properties:
+  compatible:
+    const: interrupt-counter
+
+  interrupts:
+    maxItems: 1
+
+  gpios:
+    maxItems: 1
+
+required:
+  - compatible
+
+anyOf:
+  - required: [ interrupts-extended ]
+  - required: [ interrupts ]
+  - required: [ gpios ]
+
+additionalProperties: false
+
+examples:
+  - |
+
+    #include <dt-bindings/interrupt-controller/irq.h>
+    #include <dt-bindings/gpio/gpio.h>
+
+    counter-0 {
+        compatible = "interrupt-counter";
+        interrupts-extended = <&gpio 0 IRQ_TYPE_EDGE_RISING>;
+    };
+
+    counter-1 {
+        compatible = "interrupt-counter";
+        gpios = <&gpio 2 GPIO_ACTIVE_HIGH>;
+    };
+
+    counter-2 {
+        compatible = "interrupt-counter";
+        interrupts-extended = <&gpio 2 IRQ_TYPE_EDGE_RISING>;
+        gpios = <&gpio 2 GPIO_ACTIVE_HIGH>;
+    };
+
+...