dt-bindings: mediatek: Add binding for mt8192 IOMMU

This patch adds decriptions for mt8192 IOMMU and SMI.

mt8192 also is MTK IOMMU gen2 which uses ARM Short-Descriptor translation
table format. The M4U-SMI HW diagram is as below:

                          EMI
                           |
                          M4U
                           |
                      ------------
                       SMI Common
                      ------------
                           |
  +-------+------+------+----------------------+-------+
  |       |      |      |       ......         |       |
  |       |      |      |                      |       |
larb0   larb1  larb2  larb4     ......      larb19   larb20
disp0   disp1   mdp    vdec                   IPE      IPE

All the connections are HW fixed, SW can NOT adjust it.

mt8192 M4U support 0~16GB iova range. we preassign different engines
into different iova ranges:

domain-id  module     iova-range                  larbs
   0       disp        0 ~ 4G                      larb0/1
   1       vcodec      4G ~ 8G                     larb4/5/7
   2       cam/mdp     8G ~ 12G             larb2/9/11/13/14/16/17/18/19/20
   3       CCU0    0x4000_0000 ~ 0x43ff_ffff     larb13: port 9/10
   4       CCU1    0x4400_0000 ~ 0x47ff_ffff     larb14: port 4/5

The iova range for CCU0/1(camera control unit) is HW requirement.

Signed-off-by: Yong Wu <yong.wu@mediatek.com>
Reviewed-by: Rob Herring <robh@kernel.org>
Acked-by: Krzysztof Kozlowski <krzk@kernel.org>
Reviewed-by: Tomasz Figa <tfiga@chromium.org>
Link: https://lore.kernel.org/r/20210111111914.22211-6-yong.wu@mediatek.com
Signed-off-by: Will Deacon <will@kernel.org>