dt-bindings: iio: adc: add IIO backend support

Add the generic io-backends property to the AD7779 binding to enable
support for the IIO backend framework.

Also add the adi,num-lanes property to set the number of lanes used by
AD7779.

Reviewed-by: Rob Herring (Arm) <robh@kernel.org>
Reviewed-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Signed-off-by: Ioana Risteiu <Ioana.Risteiu@analog.com>
Link: https://patch.msgid.link/20250825221355.6214-3-Ioana.Risteiu@analog.com
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>

Documentation/devicetree/bindings/iio/adc/adi,ad7779.yaml

@@ -80,11 +80,36 @@ properties:
   reset-gpios:
     maxItems: 1
 
+  io-backends:
+    maxItems: 1
+
+  adi,num-lanes:
+    description:
+      Number of lanes on which the data is sent on the output when the data
+      output interface is used.
+    $ref: /schemas/types.yaml#/definitions/uint32
+    enum: [1, 2, 4]
+    default: 4
+
 required:
   - compatible
   - reg
   - clocks
-  - interrupts
+
+allOf:
+  - if:
+      not:
+        required:
+          - io-backends
+    then:
+      properties:
+        adi,num-lanes: false
+
+oneOf:
+  - required:
+      - interrupts
+  - required:
+      - io-backends
 
 unevaluatedProperties: false
 
@@ -107,4 +132,21 @@ examples:
           clocks = <&adc_clk>;
         };
     };
+
+  - |
+    #include <dt-bindings/gpio/gpio.h>
+    spi {
+        #address-cells = <1>;
+        #size-cells = <0>;
+
+        adc@0 {
+          compatible = "adi,ad7779";
+          reg = <0>;
+          start-gpios = <&gpio0 87 GPIO_ACTIVE_LOW>;
+          reset-gpios = <&gpio0 93 GPIO_ACTIVE_LOW>;
+          clocks = <&adc_clk>;
+          io-backends = <&iio_backend>;
+          adi,num-lanes = <4>;
+        };
+    };
 ...