dt-bindings: iio: adc: ad7768-1: add new properties and checks

Add new properties:
	adi,gain-milli and adi,sync-in-spi

Signed-off-by: Jonathan Santos <Jonathan.Santos@analog.com>

Author: jonathanns

Documentation/devicetree/bindings/iio/adc/adi,ad7768-1.yaml

@@ -48,6 +48,16 @@ properties:
     description:
       ADC reference voltage supply
 
+  adi,gain-milli:
+    description: |
+      Specifies the analog anti-aliasing filter (AAF) gain applied
+      to the ADC input, in milli-units. Required for ADAQ7767-1 and
+      ADAQ7769-1 devices, the gain is determined by the pin selection
+      (IN1, IN2, IN3) on the ADAQ7767-1 or the connections of OUT_PGA
+      with IN1_AAF, IN2_AAF, or IN3_AAF on the ADAQ7769-1.
+    $ref: /schemas/types.yaml#/definitions/uint16
+    enum: [143, 364, 1000]
+
   adi,sync-in-gpios:
     maxItems: 1
     description:
@@ -56,6 +66,14 @@ properties:
       in any way, for example if the filter decimation rate changes.
       As the line is active low, it should be marked GPIO_ACTIVE_LOW.
 
+  adi,sync-in-spi:
+    description:
+      Enables synchronization of multiple devices over SPI. This property is
+      used when a signal synchronous to the base MCLK signal cannot be provided
+      via GPIO. It requires the SYNC_OUT pin to be connected to the SYNC_IN pin
+      on the ADC. In the case of multiple devices, the SYNC_OUT pin of one device
+      should be routed to the SYNC_IN pins of the other devices.
+
   reset-gpios:
     maxItems: 1
 
@@ -66,6 +84,20 @@ properties:
   "#io-channel-cells":
     const: 1
 
+allOf:
+  # Gain property only applies to ADAQ7767-1 and ADAQ7769-1 devices
+  - if:
+      properties:
+        compatible:
+          not:
+            contains:
+              enum:
+                - adi,adaq7767-1
+                - adi,adaq7769-1
+    then:
+      properties:
+        adi,gain-milli: false
+
 required:
   - compatible
   - reg
@@ -74,7 +106,21 @@ required:
   - vref-supply
   - spi-cpol
   - spi-cpha
-  - adi,sync-in-gpios
+
+allOf:
+  # adi,sync-in-gpios and adi,sync-in-spi are mutually exclusive (neither is also valid)
+  - if:
+      required:
+        - adi,sync-in-gpios
+    then:
+      properties:
+        adi,sync-in-spi: false
+  - if:
+      required:
+        - adi,sync-in-spi
+    then:
+      properties:
+        adi,sync-in-gpios: false
 
 patternProperties:
   "^channel@([0-9]|1[0-5])$":