dt-bindings:iio:resolver:adi,ad2s90: Conversion of binding to yaml.

Simple binding with a good description of why the spi-max-frequency is,
in practice not as high as the datasheet implies.  I've set the
maximum as per the value established in the description.
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Reviewed-by: Rob Herring <robh@kernel.org>
Cc: Matheus Tavares <matheus.bernardino@usp.br>
Cc: Alexandru Ardelean <alexandru.ardelean@analog.com>
Link: https://lore.kernel.org/r/20201031184854.745828-2-jic23@kernel.org

Documentation/devicetree/bindings/iio/resolver/ad2s90.txt

-Analog Devices AD2S90 Resolver-to-Digital Converter
-
-https://www.analog.com/en/products/ad2s90.html
-
-Required properties:
-  - compatible: should be "adi,ad2s90"
-  - reg: SPI chip select number for the device
-  - spi-max-frequency: set maximum clock frequency, must be 830000
-  - spi-cpol and spi-cpha:
-        Either SPI mode (0,0) or (1,1) must be used, so specify none or both of
-        spi-cpha, spi-cpol.
-
-See for more details:
-    Documentation/devicetree/bindings/spi/spi-bus.txt
-
-Note about max frequency:
-    Chip's max frequency, as specified in its datasheet, is 2Mhz. But a 600ns
-    delay is expected between the application of a logic LO to CS and the
-    application of SCLK, as also specified. And since the delay is not
-    implemented in the spi code, to satisfy it, SCLK's period should be at most
-    2 * 600ns, so the max frequency should be 1 / (2 * 6e-7), which gives
-    roughly 830000Hz.
-
-Example:
-resolver@0 {
-	compatible = "adi,ad2s90";
-	reg = <0>;
-	spi-max-frequency = <830000>;
-	spi-cpol;
-	spi-cpha;
-};

Documentation/devicetree/bindings/iio/resolver/adi,ad2s90.yaml

+# SPDX-License-Identifier: (GPL-2.0 OR BSD-2-Clause)
+%YAML 1.2
+---
+$id: http://devicetree.org/schemas/iio/resolver/adi,ad2s90.yaml#
+$schema: http://devicetree.org/meta-schemas/core.yaml#
+
+title: Analog Devices AD2S90 Resolver-to-Digital Converter
+
+maintainers:
+  - Matheus Tavares <matheus.bernardino@usp.br>
+
+description: |
+  Datasheet: https://www.analog.com/en/products/ad2s90.html
+
+properties:
+  compatible:
+    const: adi,ad2s90
+
+  reg:
+    maxItems: 1
+
+  spi-max-frequency:
+    maximum: 830000
+    description: |
+      Chip's max frequency, as specified in its datasheet, is 2Mhz. But a 600ns
+      delay is expected between the application of a logic LO to CS and the
+      application of SCLK, as also specified. And since the delay is not
+      implemented in the spi code, to satisfy it, SCLK's period should be at
+      most 2 * 600ns, so the max frequency should be 1 / (2 * 6e-7), which gives
+      roughly 830000Hz.
+
+  spi-cpol: true
+
+  spi-cpha: true
+
+additionalProperties: false
+
+required:
+  - compatible
+  - reg
+
+dependencies:
+  spi-cpol: [ spi-cpha ]
+  spi-cpha: [ spi-cpol ]
+
+examples:
+  - |
+    spi {
+        #address-cells = <1>;
+        #size-cells = <0>;
+
+        resolver@0 {
+            compatible = "adi,ad2s90";
+            reg = <0>;
+            spi-max-frequency = <830000>;
+            spi-cpol;
+            spi-cpha;
+        };
+    };
+...