dt-bindings: iio: Add KX022A accelerometer

KX022A is a 3-axis Accelerometer from ROHM/Kionix. The sensor features
include variable ODRs, I2C and SPI control, FIFO/LIFO with watermark IRQ,
tap/motion detection, wake-up & back-to-sleep events, four acceleration
ranges (2, 4, 8 and 16g) and probably some other cool features.

Add the basic device tree description for the accelerometer. Only basic
accelerometer features are considered as of now - new properties may or
may not be needed in the future when rest of the features are supported.
Signed-off-by: Matti Vaittinen <mazziesaccount@gmail.com>
Reviewed-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Link: https://lore.kernel.org/r/06f8e1ab29d02ed216db10091a269df4b6abad9a.1666614295.git.mazziesaccount@gmail.comSigned-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>

Documentation/devicetree/bindings/iio/accel/kionix,kx022a.yaml

+# SPDX-License-Identifier: GPL-2.0-only OR BSD-2-Clause
+%YAML 1.2
+---
+$id: http://devicetree.org/schemas/iio/accel/kionix,kx022a.yaml#
+$schema: http://devicetree.org/meta-schemas/core.yaml#
+
+title: ROHM/Kionix KX022A Accelerometer
+
+maintainers:
+  - Matti Vaittinen <mazziesaccount@gmail.com>
+
+description: |
+  KX022A is a 3-axis accelerometer supporting +/- 2G, 4G, 8G and 16G ranges,
+  output data-rates from 0.78Hz to 1600Hz and a hardware-fifo buffering.
+  KX022A can be accessed either via I2C or SPI.
+
+properties:
+  compatible:
+    const: kionix,kx022a
+
+  reg:
+    maxItems: 1
+
+  interrupts:
+    minItems: 1
+    maxItems: 2
+
+  interrupt-names:
+    minItems: 1
+    items:
+      - enum: [INT1, INT2]
+      - const: INT2
+
+  vdd-supply: true
+  io-vdd-supply: true
+
+  mount-matrix:
+    description: |
+      an optional 3x3 mounting rotation matrix.
+
+required:
+  - compatible
+  - reg
+  - interrupts
+
+additionalProperties: false
+
+examples:
+  - |
+    #include <dt-bindings/interrupt-controller/irq.h>
+    i2c {
+        #address-cells = <1>;
+        #size-cells = <0>;
+        accel@1f {
+            compatible = "kionix,kx022a";
+            reg = <0x1f>;
+
+            interrupt-parent = <&gpio1>;
+            interrupts = <29 IRQ_TYPE_LEVEL_LOW>;
+            interrupt-names = "INT1";
+
+            io-vdd-supply = <&iovdd>;
+            vdd-supply = <&vdd>;
+        };
+    };