dt-bindings: dma: nvidia,tegra186-gpc-dma: Add iommu-map property

Add iommu-map property to specify separate stream IDs for each DMA
channel. This enables each channel to be in its own IOMMU domain,
keeping memory isolated from other devices sharing the same DMA
controller.

Define the constraints such that if the channel and stream IDs are
contiguous, a single entry can map all the channels, but if the
channels or stream IDs are non-contiguous support multiple entries.

Signed-off-by: Akhil R <akhilrajeev@nvidia.com>
Acked-by: Rob Herring (Arm) <robh@kernel.org>
Acked-by: Thierry Reding <treding@nvidia.com>
Reviewed-by: Jon Hunter <jonathanh@nvidia.com>
Link: https://patch.msgid.link/20260331102303.33181-4-akhilrajeev@nvidia.com
Signed-off-by: Vinod Koul <vkoul@kernel.org>

Documentation/devicetree/bindings/dma/nvidia,tegra186-gpc-dma.yaml

@@ -14,6 +14,7 @@ description: |
 maintainers:
   - Jon Hunter <jonathanh@nvidia.com>
   - Rajesh Gumasta <rgumasta@nvidia.com>
+  - Akhil R <akhilrajeev@nvidia.com>
 
 properties:
   compatible:
@@ -49,6 +50,14 @@ properties:
   iommus:
     maxItems: 1
 
+  iommu-map:
+    description:
+      Maps DMA channel numbers to IOMMU stream IDs. A single entry can map all
+      channels when stream IDs are contiguous. In systems where the channels or
+      stream IDs are not contiguous, multiple entries may be needed.
+    minItems: 1
+    maxItems: 32
+
   dma-coherent: true
 
   dma-channel-mask: