[v3 0/2] pwm: add PWM driver for atcpit100

[Ben Zong-You Xie <ben717@andestech.com>]

Re-introduce the driver for atcpit100. This device driver was previously
part of the Linux Kernel, but was removed due to the deprecation of the
NDS32 architecture [1]. Although Andes now dedicates our effort on RISC-V,
ATCPIT100 is still one of our peripheral platform IPs, and that's why we
are re-introducing it now.

This patch series includes DT-bindings(1/2) and PWM driver(2/2).

The ATCPIT100 Programmable Interval Timer (PIT) is a set of compact
multi-function timers, which can be used as pulse width modulators (PWM)
as well as simple timers. ATCPIT100 supports up to 4 PIT channels,
and each PIT channel may be a simple timer or PWM, or a combination of
the timer and the PWM.

[1] https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=aec499c75cf8e0b599be4d559e6922b613085f8f
---
Changes in v3:
(1/2):
 - modify the compatible string according to Krzysztof's review.
(2/2):
 - add a check for the clock rate to prevent the overflow warning by
   kernel test robot.
 - remove the unnecessary check in .apply() reported by kernel test
   robot.

Link to v2: https://lore.kernel.org/linux-pwm/20241202060147.1271264-1-ben717@andestech.com/T/#t

Changes in v2:
(1/2):
 - change "title" in the yaml file.
 - remove vendor-specific property, and add clocks property.
(2/2):
 - add a description for hardware limitations.
 - instead of statically configuring the clock source in the dtb,
   switch the clock parent depending on the requested setting.
 - have some minor changes according to Uwe's suggestion.

Link to v1: https://lore.kernel.org/linux-pwm/20241028102721.1961289-1-ben717@andestech.com/T/#t
---
Ben Zong-You Xie (2):
  dt-bindings: pwm: add atcpit100
  pwm: atcpit100: add Andes PWM driver support

 .../bindings/pwm/andestech,atcpit100-pwm.yaml |  51 +++
 MAINTAINERS                                   |   6 +
 drivers/pwm/Kconfig                           |  17 +
 drivers/pwm/Makefile                          |   1 +
 drivers/pwm/pwm-atcpit100.c                   | 296 ++++++++++++++++++
 5 files changed, 371 insertions(+)
 create mode 100644 Documentation/devicetree/bindings/pwm/andestech,atcpit100-pwm.yaml
 create mode 100644 drivers/pwm/pwm-atcpit100.c

---
2.34.1