dt-bindings: Add bindings for Azoteq IQS620A/621/622/624/625

This patch adds device tree bindings for the Azoteq IQS620A, IQS621,
IQS622, IQS624 and IQS625 multi-function sensors.

A total of three bindings are presented (one MFD and two child nodes);
they are submitted as a single patch because the child node bindings
have no meaning in the absence of the MFD binding.

Signed-off-by: Jeff LaBundy <jeff@labundy.com>
Reviewed-by: Rob Herring <robh@kernel.org>
Signed-off-by: Lee Jones <lee.jones@linaro.org>

Documentation/devicetree/bindings/pwm/iqs620a-pwm.yaml

@@ -0,0 +1,32 @@
+# SPDX-License-Identifier: (GPL-2.0 OR BSD-2-Clause)
+%YAML 1.2
+---
+$id: http://devicetree.org/schemas/pwm/iqs620a-pwm.yaml#
+$schema: http://devicetree.org/meta-schemas/core.yaml#
+
+title: Azoteq IQS620A PWM Generator
+
+maintainers:
+  - Jeff LaBundy <jeff@labundy.com>
+
+description: |
+  The Azoteq IQS620A multi-function sensor generates a fixed-frequency PWM
+  output represented by a "pwm" child node from the parent MFD driver. See
+  Documentation/devicetree/bindings/mfd/iqs62x.yaml for further details as
+  well as an example.
+
+properties:
+  compatible:
+    enum:
+      - azoteq,iqs620a-pwm
+
+  "#pwm-cells":
+    const: 2
+
+required:
+  - compatible
+  - "#pwm-cells"
+
+additionalProperties: false
+
+...