dt-bindings:iio:accel:adis16201 and adis16209 bindings

These two devices have different internal characteristics, but their
external connectivity and as a result device tree descriptions are
identical.

Note that neither driver in Linux currently has an of_match_table
but instead rely on matching via name alone.
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Reviewed-by: Rob Herring <robh@kernel.org>
Link: https://lore.kernel.org/r/20210401174112.320497-2-jic23@kernel.org

Documentation/devicetree/bindings/iio/accel/adi,adis16201.yaml

+# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
+%YAML 1.2
+---
+$id: http://devicetree.org/schemas/iio/accel/adi,adis16201.yaml#
+$schema: http://devicetree.org/meta-schemas/core.yaml#
+
+title: ADIS16201 Dual Axis Inclinometer and similar
+
+maintainers:
+  - Jonathan Cameron <Jonathan.Cameron@huawei.com>
+
+description: |
+  Two similar parts from external interface point of view.
+  SPI interface.
+    https://www.analog.com/en/products/adis16201.html
+    https://www.analog.com/en/products/adis16209.html
+
+properties:
+  compatible:
+    enum:
+      - adi,adis16201
+      - adi,adis16209
+
+  reg:
+    maxItems: 1
+
+  interrupts:
+    maxItems: 1
+
+  spi-max-frequency: true
+
+  vdd-supply: true
+
+required:
+  - compatible
+  - reg
+
+additionalProperties: false
+
+examples:
+  - |
+    #include <dt-bindings/interrupt-controller/irq.h>
+    spi0 {
+        #address-cells = <1>;
+        #size-cells = <0>;
+
+        accelerometer@0 {
+            compatible = "adi,adis16201";
+            reg = <0>;
+            spi-max-frequency = <2500000>;
+            interrupt-parent = <&gpio0>;
+            interrupts = <0 IRQ_TYPE_LEVEL_HIGH>;
+        };
+    };
+...