dt-bindings: net: add IPA iommus property

The IPA accesses "IMEM" and main system memory through an SMMU, so
its DT node requires an iommus property to define range of stream IDs
it uses.

Signed-off-by: Alex Elder <elder@linaro.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

Documentation/devicetree/bindings/net/qcom,ipa.yaml

@@ -20,7 +20,10 @@ description:
   The GSI is an integral part of the IPA, but it is logically isolated
   and has a distinct interrupt and a separately-defined address space.
 
-  See also soc/qcom/qcom,smp2p.txt and interconnect/interconnect.txt.
+  See also soc/qcom/qcom,smp2p.txt and interconnect/interconnect.txt.  See
+  iommu/iommu.txt and iommu/arm,smmu.yaml for more information about SMMU
+  bindings.
+
 
   - |
     --------             ---------
@@ -54,6 +57,9 @@ properties:
       - const: ipa-shared
       - const: gsi
 
+  iommus:
+    maxItems: 1
+
   clocks:
     maxItems: 1
 
@@ -126,6 +132,7 @@ properties:
 
 required:
   - compatible
+  - iommus
   - reg
   - clocks
   - interrupts
@@ -164,6 +171,7 @@ examples:
                 modem-init;
                 modem-remoteproc = <&mss_pil>;
 
+                iommus = <&apps_smmu 0x720 0x3>;
                 reg = <0 0x1e40000 0 0x7000>,
                         <0 0x1e47000 0 0x2000>,
                         <0 0x1e04000 0 0x2c000>;