spi: dt-bindings: tegra: Document IOMMU property for Tegra234 QSPI

Add the 'iommus' property to the Tegra QSPI device tree binding.
The property is needed for Tegra234 when using the internal DMA
controller, and is not supported on other Tegra chips, as DMA is
handled by an external controller.

Signed-off-by: Vishwaroop A <[email protected]>
Acked-by: Conor Dooley <[email protected]>
Reviewed-by: Jon Hunter <[email protected]>
Link: https://patch.msgid.link/[email protected]
Signed-off-by: Mark Brown <[email protected]>

Author: Vishwaroop A

Documentation/devicetree/bindings/spi/nvidia,tegra210-quad.yaml

@@ -10,9 +10,6 @@ maintainers:
   - Thierry Reding <[email protected]>
   - Jonathan Hunter <[email protected]>
 
-allOf:
-  - $ref: spi-controller.yaml#
-
 properties:
   compatible:
     enum:
@@ -47,6 +44,9 @@ properties:
       - const: rx
       - const: tx
 
+  iommus:
+    maxItems: 1
+
 patternProperties:
   "@[0-9a-f]+$":
     type: object
@@ -69,6 +69,18 @@ required:
 
 unevaluatedProperties: false
 
+allOf:
+  - $ref: spi-controller.yaml#
+  - if:
+      properties:
+        compatible:
+          not:
+            contains:
+              const: nvidia,tegra234-qspi
+    then:
+      properties:
+        iommus: false
+
 examples:
   - |
     #include <dt-bindings/clock/tegra210-car.h>