A gpio-locked fixed clock aggregates one or more input clocks and/or one
or more GPIOs. It's similar to a gated-fixed-clock, but GPIO direction is
inverted. Consumers can use the output clock to wait until all input
clocks are locked and only then initialize / access dependent peripherals.

The usage example for such a driver is when peripherals depend on PLLs in
a FPGA, which can't be directly accessed by the CPU, but need a GPIO pin
to check whether clock is actually usable. E.g. some of the IPs might not
have a proper split between registers and IP core, which means that if an
external clock and/or PLL lock is missing and one tries to access the 
registers, the response never comes, thus the CPU stalls.

Signed-off-by: Vyacheslav Yurkov <uvv.mail@gmail.com>
Signed-off-by: Vyacheslav Yurkov <V.Yurkov.EXT@bruker.com>
---
Changes in v3:
- Removed unnecessary dt bindings
- Improved HW description and commit messages
- Link to v2: https://lore.kernel.org/r/20260510-feature-clock-guard-v2-0-6c25458d5340@bruker.com

Changes in v2:
- Renamed to clk-gpio-locked to express intent.
- Provide enable() / is_enabled() operations so the clock behaves as
  expected
- Fixed DTS errors / warnings
- Link to v1: https://lore.kernel.org/r/20260318-feature-clock-guard-v1-0-6137cb4084b7@bruker.com

---
Vyacheslav Yurkov (2):
      dt-bindings: Add GPIO-locked fixed clock
      clk: Add gpio-locked fixed clock driver

 .../bindings/clock/gpio-locked-fixed-clock.yaml    |  70 +++++
 drivers/clk/Makefile                               |   1 +
 drivers/clk/clk-gpio-locked.c                      | 306 +++++++++++++++++++++
 3 files changed, 377 insertions(+)
---
base-commit: ba3e43a9e601636f5edb54e259a74f96ca3b8fd8
change-id: 20260318-feature-clock-guard-f20a2c35b965

Best regards,
-- 
Vyacheslav Yurkov <V.Yurkov.EXT@bruker.com>