dt-bindings: iio: dac: ad5696: add reset/ldac/gain support

Add GPIO property for RESET, LDAC and GAIN pin. RESET is active-low, LDAC
is used to load DAC channels with values from input registers and GAIN
can double the voltage in output channels. The gain-gpios property is
not available to all supported parts. The adi,range-double property
indicates that GAIN pin is hardwired to high in case gain-gpios is not
set, otherwise it sets the initial value for the gain setting.

Acked-by: Conor Dooley <conor.dooley@microchip.com>
Signed-off-by: Rodrigo Alencar <rodrigo.alencar@analog.com>
Signed-off-by: Jonathan Cameron <jic23@kernel.org>

Documentation/devicetree/bindings/iio/dac/adi,ad5696.yaml

@@ -37,14 +37,52 @@ properties:
     description: |
       The regulator supply for DAC reference voltage.
 
+  reset-gpios:
+    description: Active-low RESET pin to reset the device.
+    maxItems: 1
+
+  ldac-gpios:
+    description:
+      Active-low LDAC pin used to asynchronously update the DAC channels.
+    maxItems: 1
+
+  gain-gpios:
+    description:
+      GAIN pin that sets a multiplier for the DAC output voltage. When high,
+      the DAC output voltage is multiplied by 2, otherwise it is unchanged.
+    maxItems: 1
+
+  adi,range-double:
+    description:
+      Sets the initial voltage output range from 0 to 2xVREF. On devices that
+      have a GAIN pin and no gain-gpios property is set, this indicates the pin
+      is hardwired high.
+    type: boolean
+
 required:
   - compatible
   - reg
 
+allOf:
+  - if:
+      properties:
+        compatible:
+          contains:
+            enum:
+              - adi,ad5311r
+              - adi,ad5691r
+              - adi,ad5692r
+              - adi,ad5693
+              - adi,ad5693r
+    then:
+      properties:
+        gain-gpios: false
+
 additionalProperties: false
 
 examples:
   - |
+    #include <dt-bindings/gpio/gpio.h>
     i2c {
       #address-cells = <1>;
       #size-cells = <0>;
@@ -53,6 +91,7 @@ examples:
         compatible = "adi,ad5696";
         reg = <0>;
         vcc-supply = <&dac_vref>;
+        ldac-gpios = <&gpio0 1 GPIO_ACTIVE_LOW>;
       };
     };
 ...