dt-bindings: iio: adc: ti,ads7950 binding conversion

Conversion from txt to yaml.  The binding documents that
as not all boards will make use of the ADC channels via a consumer
driver.  It does no harm however, so we will leave it as required.
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Reviewed-by: Rob Herring <robh@kernel.org>
Reviewed-by: David Lechner <david@lechnology.com>
Cc: David Lechner <david@lechnology.com>
Link: https://lore.kernel.org/r/20200830161154.3201-3-jic23@kernel.org

Documentation/devicetree/bindings/iio/adc/ti,ads7950.yaml

+# SPDX-License-Identifier: (GPL-2.0 OR BSD-2-Clause)
+%YAML 1.2
+---
+$id: http://devicetree.org/schemas/iio/adc/ti,ads7950.yaml#
+$schema: http://devicetree.org/meta-schemas/core.yaml#
+
+title: Texas Instruments ADS7950 and similar ADCs
+
+maintainers:
+  - David Lechner <david@lechnology.com>
+
+description: |
+  Family of 4-16 channel, 8-12 bit ADCs with SPI interface.
+
+properties:
+  compatible:
+    enum:
+      - ti,ads7950
+      - ti,ads7951
+      - ti,ads7952
+      - ti,ads7953
+      - ti,ads7954
+      - ti,ads7955
+      - ti,ads7956
+      - ti,ads7957
+      - ti,ads7958
+      - ti,ads7959
+      - ti,ads7960
+      - ti,ads7961
+
+  reg:
+    maxItems: 1
+
+  spi-max-frequency:
+    maximum: 20000000
+
+  vref-supply:
+    description: Supplies the 2.5V or 5V reference voltage
+
+  "#io-channel-cells":
+    const: 1
+
+required:
+  - compatible
+  - reg
+  - vref-supply
+  - "#io-channel-cells"
+
+additionalProperties: false
+
+examples:
+  - |
+    spi {
+        #address-cells = <1>;
+        #size-cells = <0>;
+
+        adc@0 {
+            compatible = "ti,ads7957";
+            reg = <0>;
+            vref-supply = <&refin_supply>;
+            spi-max-frequency = <10000000>;
+            #io-channel-cells = <1>;
+        };
+    };
+...

Documentation/devicetree/bindings/iio/adc/ti-ads7950.txt

-* Texas Instruments ADS7950 family of A/DC chips
-
-Required properties:
- - compatible: Must be one of "ti,ads7950", "ti,ads7951", "ti,ads7952",
-   "ti,ads7953", "ti,ads7954", "ti,ads7955", "ti,ads7956", "ti,ads7957",
-   "ti,ads7958", "ti,ads7959", "ti,ads7960", or "ti,ads7961"
- - reg: SPI chip select number for the device
- - #io-channel-cells: Must be 1 as per ../iio-bindings.txt
- - vref-supply: phandle to a regulator node that supplies the 2.5V or 5V
-   reference voltage
-
-Recommended properties:
- - spi-max-frequency: Definition as per
-		Documentation/devicetree/bindings/spi/spi-bus.txt
-
-Example:
-adc@0 {
-	compatible = "ti,ads7957";
-	reg = <0>;
-	#io-channel-cells = <1>;
-	vref-supply = <&refin_supply>;
-	spi-max-frequency = <10000000>;
-};