So far our parsing of {iommu,msi}-map properites has always blindly
assumed that the output specifiers will always have exactly 1 cell.
This typically does happen to be the case, but is not actually enforced
(and the PCI msi-map binding even explicitly states support for 0 or 1
cells) - as a result we've now ended up with dodgy DTs out in the field
which depend on this behaviour to map a 1-cell specifier for a 2-cell
provider, despite that being bogus per the bindings themselves.

Since there is some potential use[1] in being able to map at least
single input IDs to multi-cell output specifiers (and properly support
0-cell outputs as well), add support for properly parsing and using the
target nodes' #cells values, albeit with the unfortunate complication of
still having to work around expectations of the old behaviour too.
							-- Robin.

Unlike single #{}-cell, it is complex to establish a linear relation
between input 'id' and output specifier for multi-cell properties, thus
it is always expected that len never going to be > 1. 

These changes have been tested on QEMU for the arm64 architecture.

[1] https://lore.kernel.org/all/20250627-video_cb-v3-0-51e18c0ffbce@quicinc.com/

V9:
  - Updated TO/CC list based on feedback to include all relevant
    maintainers.
  - No functional changes to the patches themselves.

  Link to V8:
  https://lore.kernel.org/all/20260226074245.3098486-1-vijayanand.jitta@oss.qualcomm.com/

V8:
  - Removed mentions of of_map_args from commit message to match code.

  Link to V7:
  https://lore.kernel.org/all/20260210101157.2145113-1-vijayanand.jitta@oss.qualcomm.com/

V7:
  - Removed of_map_id_args structure and replaced it with
    of_phandle_args as suggested by Dmitry.

  Link to V6:
  https://lore.kernel.org/all/20260121055400.937856-1-vijayanand.jitta@oss.qualcomm.com/

V6:
  - Fixed build error reported by kernel test bot.

  Link to V5:
  https://lore.kernel.org/all/20260118181125.1436036-1-vijayanand.jitta@oss.qualcomm.com/

V5:
  - Fixed Build Warnings.
  - Raised PR for iommu-map dtschema: https://github.com/devicetree-org/dt-schema/pull/184

  Link to V4:
  https://lore.kernel.org/all/20251231114257.2382820-1-vijayanand.jitta@oss.qualcomm.com/

V4:
  - Added Reviewed-by tag.
  - Resolved warnings reported by kernel test bot, minor code
    reorganization.

  Link to V3:
  https://lore.kernel.org/all/20251221213602.2413124-1-vijayanand.jitta@oss.qualcomm.com/

V3:
  - Added Reviewed-by tag.
  - Updated of_map_id_args struct as a wrapper to of_phandle_args and
    added comment description as suggested by Rob Herring.

  Link to V2:
  https://lore.kernel.org/all/20251204095530.8627-1-vijayanand.jitta@oss.qualcomm.com/

V2:
  - Incorporated the patches from Robin that does the clean implementation.
  - Dropped the patches the were adding multi-map support from this series
    as suggested.

V1:
 https://lore.kernel.org/all/cover.1762235099.git.charan.kalla@oss.qualcomm.com/

RFC:
 https://lore.kernel.org/all/20250928171718.436440-1-charan.kalla@oss.qualcomm.com/#r

Signed-off-by: Vijayanand Jitta <vijayanand.jitta@oss.qualcomm.com>
---
Charan Teja Kalla (1):
      of: factor arguments passed to of_map_id() into a struct

Robin Murphy (2):
      of: Add convenience wrappers for of_map_id()
      of: Respect #{iommu,msi}-cells in maps

 drivers/cdx/cdx_msi.c                    |   3 +-
 drivers/iommu/of_iommu.c                 |   6 +-
 drivers/irqchip/irq-gic-its-msi-parent.c |   2 +-
 drivers/of/base.c                        | 148 ++++++++++++++++++++++---------
 drivers/of/irq.c                         |   3 +-
 drivers/pci/controller/dwc/pci-imx6.c    |  12 ++-
 drivers/pci/controller/pcie-apple.c      |   5 +-
 drivers/xen/grant-dma-ops.c              |   3 +-
 include/linux/of.h                       |  33 +++++--
 9 files changed, 152 insertions(+), 63 deletions(-)
---
base-commit: 3fa5e5702a82d259897bd7e209469bc06368bf31
change-id: 20260301-parse_iommu_cells-1c33768aebba

Best regards,
-- 
Vijayanand Jitta <vijayanand.jitta@oss.qualcomm.com>