dt-bindings: qcom: geni-se: document I2C Master Hub wrapper variant

The I2C Master Hub is a stripped down version of the GENI Serial Engine
QUP Wrapper Controller but only supporting I2C serial engines without
DMA support.

Document the variant compatible, forbid UART and SPI sub-nodes,
and remove requirement for the Master AHB clock and iommu property.
Signed-off-by: Neil Armstrong <neil.armstrong@linaro.org>
Reviewed-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Signed-off-by: Wolfram Sang <wsa@kernel.org>

Documentation/devicetree/bindings/soc/qcom/qcom,geni-se.yaml

@@ -21,20 +21,19 @@ properties:
   compatible:
     enum:
       - qcom,geni-se-qup
+      - qcom,geni-se-i2c-master-hub
 
   reg:
     description: QUP wrapper common register address and length.
     maxItems: 1
 
   clock-names:
-    items:
-      - const: m-ahb
-      - const: s-ahb
+    minItems: 1
+    maxItems: 2
 
   clocks:
-    items:
-      - description: Master AHB Clock
-      - description: Slave AHB Clock
+    minItems: 1
+    maxItems: 2
 
   "#address-cells":
     const: 2
@@ -81,6 +80,39 @@ patternProperties:
     description: GENI Serial Engine based UART Controller.
     $ref: /schemas/serial/qcom,serial-geni-qcom.yaml#
 
+allOf:
+  - if:
+      properties:
+        compatible:
+          contains:
+            const: qcom,geni-se-i2c-master-hub
+    then:
+      properties:
+        clock-names:
+          items:
+            - const: s-ahb
+
+        clocks:
+          items:
+            - description: Slave AHB Clock
+
+        iommus: false
+
+      patternProperties:
+        "spi@[0-9a-f]+$": false
+        "serial@[0-9a-f]+$": false
+    else:
+      properties:
+        clock-names:
+          items:
+            - const: m-ahb
+            - const: s-ahb
+
+        clocks:
+          items:
+            - description: Master AHB Clock
+            - description: Slave AHB Clock
+
 additionalProperties: false
 
 examples: