Document how the generic "iommus" binding should be used to describe ARM
SMMU stream IDs instead of the old "mmu-masters" binding.
Acked-by: NRob Herring <robh@kernel.org>
Signed-off-by: NRobin Murphy <robin.murphy@arm.com>
Signed-off-by: NWill Deacon <will.deacon@arm.com>