dt-bindings: iio: adc: adi,ad4000: Add PulSAR

Extend the AD4000 series device tree documentation to also describe
PulSAR devices.

The single-channel series of PulSAR devices is similar to the AD4000 series
except PulSAR devices sample at slower rates and don't have a
configuration register. Because PulSAR devices don't have a configuration
register, they don't support all features of AD4000 devices and thus fewer
interfaces are provided to user space. Also, while AD4000 may have their
SDI pin connected to SPI host MOSI line, PulSAR SDI pin is never connected
to MOSI.

Some devices within the PulSAR series are just faster versions of others.
>From fastest to slowest, AD7980, AD7988-5, AD7686, AD7685, and AD7988-1 are
all 16-bit pseudo-differential pin-for-pin compatible ADCs. Devices that
only vary on the sample rate are documented with a common fallback
compatible.

Signed-off-by: Marcelo Schmitt <marcelo.schmitt@analog.com>
Reviewed-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Link: https://patch.msgid.link/cc05f1471c409ab38722cd0e80fd5857ff9ce5db.1733147444.git.marcelo.schmitt@analog.com
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>

Documentation/devicetree/bindings/iio/adc/adi,ad4000.yaml

@@ -19,49 +19,82 @@ description: |
     https://www.analog.com/media/en/technical-documentation/data-sheets/ad4020-4021-4022.pdf
     https://www.analog.com/media/en/technical-documentation/data-sheets/adaq4001.pdf
     https://www.analog.com/media/en/technical-documentation/data-sheets/adaq4003.pdf
+    https://www.analog.com/media/en/technical-documentation/data-sheets/ad7685.pdf
+    https://www.analog.com/media/en/technical-documentation/data-sheets/ad7686.pdf
+    https://www.analog.com/media/en/technical-documentation/data-sheets/ad7687.pdf
+    https://www.analog.com/media/en/technical-documentation/data-sheets/ad7688.pdf
+    https://www.analog.com/media/en/technical-documentation/data-sheets/ad7690.pdf
+    https://www.analog.com/media/en/technical-documentation/data-sheets/ad7691.pdf
+    https://www.analog.com/media/en/technical-documentation/data-sheets/ad7693.pdf
+    https://www.analog.com/media/en/technical-documentation/data-sheets/ad7942.pdf
+    https://www.analog.com/media/en/technical-documentation/data-sheets/ad7946.pdf
+    https://www.analog.com/media/en/technical-documentation/data-sheets/ad7980.pdf
+    https://www.analog.com/media/en/technical-documentation/data-sheets/ad7982.pdf
+    https://www.analog.com/media/en/technical-documentation/data-sheets/ad7983.pdf
+    https://www.analog.com/media/en/technical-documentation/data-sheets/ad7984.pdf
+    https://www.analog.com/media/en/technical-documentation/data-sheets/ad7988-1_7988-5.pdf
 
 $ref: /schemas/spi/spi-peripheral-props.yaml#
 
 properties:
   compatible:
     oneOf:
-      - const: adi,ad4000
+      - enum:
+          - adi,ad4000
+          - adi,ad4001
+          - adi,ad4002
+          - adi,ad4003
+          - adi,ad4020
+          - adi,adaq4001
+          - adi,adaq4003
+          - adi,ad7687
+          - adi,ad7691
+          - adi,ad7942
+          - adi,ad7946
+          - adi,ad7983
       - items:
           - enum:
               - adi,ad4004
               - adi,ad4008
           - const: adi,ad4000
-
-      - const: adi,ad4001
       - items:
           - enum:
               - adi,ad4005
           - const: adi,ad4001
-
-      - const: adi,ad4002
       - items:
           - enum:
               - adi,ad4006
               - adi,ad4010
           - const: adi,ad4002
-
-      - const: adi,ad4003
       - items:
           - enum:
               - adi,ad4007
               - adi,ad4011
           - const: adi,ad4003
-
-      - const: adi,ad4020
       - items:
           - enum:
               - adi,ad4021
               - adi,ad4022
           - const: adi,ad4020
-
-      - const: adi,adaq4001
-
-      - const: adi,adaq4003
+      - items:
+          - enum:
+              - adi,ad7685
+              - adi,ad7686
+              - adi,ad7980
+              - adi,ad7988-1
+              - adi,ad7988-5
+          - const: adi,ad7983
+      - items:
+          - enum:
+              - adi,ad7688
+              - adi,ad7693
+          - const: adi,ad7687
+      - items:
+          - enum:
+              - adi,ad7690
+              - adi,ad7982
+              - adi,ad7984
+          - const: adi,ad7691
 
   reg:
     maxItems: 1
@@ -133,6 +166,22 @@ required:
   - ref-supply
 
 allOf:
+  # Single-channel PulSAR devices have SDI either tied to VIO, GND, or host CS.
+  - if:
+      properties:
+        compatible:
+          contains:
+            enum:
+              - adi,ad7687
+              - adi,ad7691
+              - adi,ad7942
+              - adi,ad7946
+              - adi,ad7983
+    then:
+      properties:
+        adi,sdi-pin:
+          enum: [ high, low, cs ]
+          default: cs
   # The configuration register can only be accessed if SDI is connected to MOSI
   - if:
       required: