[PATCH V4 1/2] dt-bindings: spi: tegra: Document IOMMU property for Tegra234 QSPI

[Vishwaroop A <va@nvidia.com>]

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 <va@nvidia.com>
---
 .../bindings/spi/nvidia,tegra210-quad.yaml     | 18 +++++++++++++++---
 1 file changed, 15 insertions(+), 3 deletions(-)

Changes since v3:
- Inverted the logic of the conditional statement for the IOMMU property

Changes since v2:
- Fixed version number to match the actual version
- Added proper changelog section
- No functional changes from v2

Changes since v1:
- Fixed subject prefix to match subsystem (dt-bindings: spi: tegra)
- Improved commit message formatting to follow Linux coding style
- Clarified that IOMMU is only required for Tegra234 platform
- Added explicit disallow for IOMMU on other platforms
- Removed redundant explanations of what the patch does
- Fixed commit message to use imperative mood

Initial Version:
- Initial implementation of IOMMU property documentation
- Added iommus property to device tree binding
- Added support for Tegra234 platform
- Added explanation of DMA and IOMMU requirements

diff --git a/Documentation/devicetree/bindings/spi/nvidia,tegra210-quad.yaml b/Documentation/devicetree/bindings/spi/nvidia,tegra210-quad.yaml
index 48e97e240265..8b3640280559 100644
--- a/Documentation/devicetree/bindings/spi/nvidia,tegra210-quad.yaml
+++ b/Documentation/devicetree/bindings/spi/nvidia,tegra210-quad.yaml
@@ -10,9 +10,6 @@ maintainers:
   - Thierry Reding <thierry.reding@gmail.com>
   - Jonathan Hunter <jonathanh@nvidia.com>
 
-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>
-- 
2.17.1