[PATCH RFC 0/2] of: property: Make fw_devlink follow GPIO and PWM nexus maps

[Ernest Van Hoecke <ernestvanhoecke@gmail.com>]

This series fixes an fw_devlink supplier-resolution problem reported by
Leonardo Costa while using a Devicetree nexus to describe GPIO and PWM
resources routed through an LVDS connector. Consumers referencing the
nexus could remain deferred because fw_devlink linked them to the nexus
rather than to the providers selected by gpio-map and pwm-map. [1]

GPIO and PWM consumer APIs use of_parse_phandle_with_args_map() to
resolve specifiers through gpio-map and pwm-map properties. The
corresponding fw_devlink parsers use direct phandle parsing instead.
Given a consumer which references a nexus, the consumer API and
fw_devlink therefore resolve the reference to different nodes:

  consumer API:  consumer -> nexus -> mapped provider
  fw_devlink:    consumer -> nexus

A nexus is a translation node rather than the resource provider and need
not have a driver. The link to it can consequently remain unresolved and
defer the consumer even though the mapped provider is available.

Make the fw_devlink GPIO and PWM parsers use the same map-aware resolver
as their consumer APIs. The resolver also handles valid direct
references by returning the original provider when no map is present.
Use dedicated exact-name and suffix declaration macros to opt these
bindings into map-aware parsing without changing unrelated property
parsers. Retain GPIO's existing exclusions and compatibility handling.

The regression tests call the OF add_links operation and verify that a
mapped reference creates exactly one link to the final provider, not to
the nexus. They also cover valid direct references. The GPIO tests
exercise all property spellings recognized by fw_devlink, including the
deprecated singular and unprefixed forms.

Tested with:
  - The new CONFIG_OF_UNITTEST fw_devlink cases under QEMU/x86_64 all
    passed
  - W=1 builds on x86_64 and arm64, including the OF unittest data
  - Toradex Verdin iMX8M Plus hardware using a connector nexus for the
    display GPIO and PWM resources: the display probes successfully

Sending as an RFC because the unittest part can use some polish, but I
wanted to gather feedback on the direction before doing so.

[1] https://lore.kernel.org/all/juuc4af7ndbajcl7gzf4tg5qz2q2j5tt3rvql4jbauradujrre@gc5nbdhhixaf/

Signed-off-by: Ernest Van Hoecke <ernest.vanhoecke@toradex.com>

---
Ernest Van Hoecke (2):
      of: property: fw_devlink: Follow GPIO nexus maps
      of: property: fw_devlink: Follow PWM nexus maps

 drivers/of/property.c                       | 49 +++++++++++++++-----
 drivers/of/unittest-data/tests-phandle.dtsi | 49 ++++++++++++++++++++
 drivers/of/unittest.c                       | 71 +++++++++++++++++++++++++++++
 3 files changed, 158 insertions(+), 11 deletions(-)
---
base-commit: cee9395acd8043be0644b25c34bfa86623f2b935
change-id: 20260901-fw-devlink-nexus-ready-c859706b019d

Best regards,
-- 
Ernest Van Hoecke <ernest.vanhoecke@toradex.com>