dt-bindings: iio: adc: ad7476: Add ROHM bd79105

The ROHM BD79105 is a simple, 16-bit, 1-channel ADC with a 'CONVSTART'
pin used to start the ADC conversion. Other than the 'CONVSTART', there
are 3 supply pins (one used as a reference), analog inputs, ground and
communication pins. It's worth noting that the pin somewhat confusingly
labeled as 'DIN', is a pin which should be used as a chip-select. The IC
does not have any writable registers.

The device is designed so that the output pin can, in addition to
outputting the data, be used as a 'data-ready'-IRQ. There are cases
where the IRQ can't be used (because it is delivered via SPI data-line).
Hence, some systems may use a GPIO for polling the data readiness.

Add a compatible for the bd79105 and add the data-ready GPIO to the
binding.

Signed-off-by: Matti Vaittinen <[e-mail]>
Reviewed-by: Krzysztof Kozlowski <[e-mail]>
Link: https://patch.msgid.link/3f70f6[e-mail]
Signed-off-by: Jonathan Cameron <[e-mail]>

Documentation/devicetree/bindings/iio/adc/adi,ad7476.yaml

···
               - adi,ad7910
               - adi,ad7920
               - adi,ad7940
+              - rohm,bd79105
               - ti,adc081s
               - ti,adc101s
               - ti,adc121s
···
           - const: ti,ads7866
 
   reg:
+    maxItems: 1
+
+  interrupts:
+    description:
+      The data-ready interrupt. Provided via DOUT pin.
     maxItems: 1
 
   vcc-supply:
···
     description: A GPIO used to trigger the start of a conversion
     maxItems: 1
 
+  rdy-gpios:
+    description: A GPIO for detecting the data-ready.
+    maxItems: 1
+
 required:
   - compatible
   - reg
 
 allOf:
   - $ref: /schemas/spi/spi-peripheral-props.yaml#
+
+# Devices with an IRQ
+  - if:
+      properties:
+        compatible:
+          contains:
+            enum:
+              - rohm,bd79105
+    then:
+      properties:
+        interrupts: true
+    else:
+      properties:
+        interrupts: false
 
   # Devices where reference is vcc
   - if:
···
                 - adi,ad7274
                 - adi,ad7475
                 - lltc,ltc2314-14
+                - rohm,bd79105
     then:
       properties:
         vref-supply: false
···
               - adi,ad7274
               - adi,ad7475
               - lltc,ltc2314-14
+              - rohm,bd79105
     then:
       required:
         - vref-supply
···
               enum:
                 - adi,ad7475
                 - adi,ad7495
+                - rohm,bd79105
     then:
       properties:
         vdrive-supply: false
+
+  # Devices which support polling the data-ready via GPIO
+  - if:
+      not:
+        properties:
+          compatible:
+            contains:
+              enum:
+                - rohm,bd79105
+    then:
+      properties:
+        rdy-gpios: false
+
   - if:
       not:
         properties:
···
               enum:
                 - adi,ad7091
                 - adi,ad7091r
+                - rohm,bd79105
     then:
       properties:
         adi,conversion-start-gpios: false
+
+  # Devices with a convstart GPIO where it is not optional
+  - if:
+      properties:
+        compatible:
+          contains:
+            enum:
+              - rohm,bd79105
+    then:
+      required:
+        - adi,conversion-start-gpios
 
 unevaluatedProperties: false