Documentation: fsl-mc: add iommu-map device-tree binding for fsl-mc bus

The existing IOMMU bindings cannot be used to specify the relationship
between fsl-mc devices and IOMMUs. This patch adds a generic binding for
mapping fsl-mc devices to IOMMUs, using iommu-map property.
Signed-off-by: Nipun Gupta <nipun.gupta@nxp.com>
Reviewed-by: Rob Herring <robh@kernel.org>
Acked-by: Robin Murphy <robin.murphy@arm.com>
Signed-off-by: Joerg Roedel <jroedel@suse.de>

Documentation/devicetree/bindings/misc/fsl,qoriq-mc.txt

@@ -9,6 +9,25 @@ blocks that can be used to create functional hardware objects/devices
 such as network interfaces, crypto accelerator instances, L2 switches,
 etc.
 
+For an overview of the DPAA2 architecture and fsl-mc bus see:
+Documentation/networking/dpaa2/overview.rst
+
+As described in the above overview, all DPAA2 objects in a DPRC share the
+same hardware "isolation context" and a 10-bit value called an ICID
+(isolation context id) is expressed by the hardware to identify
+the requester.
+
+The generic 'iommus' property is insufficient to describe the relationship
+between ICIDs and IOMMUs, so an iommu-map property is used to define
+the set of possible ICIDs under a root DPRC and how they map to
+an IOMMU.
+
+For generic IOMMU bindings, see
+Documentation/devicetree/bindings/iommu/iommu.txt.
+
+For arm-smmu binding, see:
+Documentation/devicetree/bindings/iommu/arm,smmu.txt.
+
 Required properties:
 
     - compatible
@@ -88,14 +107,34 @@ Sub-nodes:
               Value type: <phandle>
               Definition: Specifies the phandle to the PHY device node associated
                           with the this dpmac.
+Optional properties:
+
+- iommu-map: Maps an ICID to an IOMMU and associated iommu-specifier
+  data.
+
+  The property is an arbitrary number of tuples of
+  (icid-base,iommu,iommu-base,length).
+
+  Any ICID i in the interval [icid-base, icid-base + length) is
+  associated with the listed IOMMU, with the iommu-specifier
+  (i - icid-base + iommu-base).
 
 Example:
 
+        smmu: iommu@5000000 {
+               compatible = "arm,mmu-500";
+               #iommu-cells = <1>;
+               stream-match-mask = <0x7C00>;
+               ...
+        };
+
         fsl_mc: fsl-mc@80c000000 {
                 compatible = "fsl,qoriq-mc";
                 reg = <0x00000008 0x0c000000 0 0x40>,    /* MC portal base */
                       <0x00000000 0x08340000 0 0x40000>; /* MC control reg */
                 msi-parent = <&its>;
+                /* define map for ICIDs 23-64 */
+                iommu-map = <23 &smmu 23 41>;
                 #address-cells = <3>;
                 #size-cells = <1>;