boards/arm/ht32f491x3: Add PWM support for the HT32F49163 Starter Kit board

[FelipeMdeO]

Summary

This PR adds PWM support for the HT32F491x3 ESK32 board.

Changes included:

add HT32F491x3 TMR3 PWM lower-half driver support
register /dev/pwm0 on the ESK32 board
add board-level PWM pin mapping for TMR3 channels 1 to 4
add esk32:pwm configuration for board-level PWM validation
document PWM support, pin mapping, and test procedure for ESK32

Impact

Is new feature added? Yes
Impact on user: esk32:pwm now provides /dev/pwm0 and the pwm example application for board-level PWM testing
Impact on build: No global build changes
Impact on hardware: Yes, ARM/HT32F491x3 ESK32 board support
Impact on documentation: Yes
Impact on security: No

Testing

./tools/configure.sh -l esk32:pwm
make olddefconfig
make -j all
/dev/pwm0 registered successfully
PWM generation tested by invoking the pwm example from NSH
command used: `pwm -f 1000 -d 50 -t 5`
PWM output probed on PA6 with a logic analyzer
1 kHz PWM generated on PA6 with 50% duty cycle as expected
PWM start and stop behavior matched the requested command duration

[FelipeMdeO]

Hello @xiaoxiang781216 , @acassis , @linguini1 . I am working with this board daily, so I am porting drivers step by step.
I hope add pwm, pulse counter, i2c, dma and usb drivers during the next weeks.

[simbit18]

Hi @FelipeMdeO please fix

====================================================================================
Configuration/Tool: esk32/pwm,CONFIG_ARM_TOOLCHAIN_GNU_EABI
2026-03-30 03:54:15
------------------------------------------------------------------------------------
  Cleaning...
  Configuring...
  Disabling CONFIG_ARM_TOOLCHAIN_GNU_EABI
  Enabling CONFIG_ARM_TOOLCHAIN_GNU_EABI
  Building NuttX...
  [1/1] Normalize esk32/pwm
24,26d23
< CONFIG_EXAMPLES_PWM_DEVPATH="/dev/pwm0"
< CONFIG_EXAMPLES_PWM_DUTYPCT=50
< CONFIG_EXAMPLES_PWM_DURATION=5
33d29
< CONFIG_HT32F491X3_TMR3_CHANNEL=1
Saving the new configuration file
HEAD detached at pull/18649/merge
Changes not staged for commit:
  (use "git add <file>..." to update what will be committed)
  (use "git restore <file>..." to discard changes in working directory)
	modified:   boards/arm/ht32f491x3/esk32/configs/pwm/defconfig

no changes added to commit (use "git add" and/or "git commit -a")
====================================================================================

[FelipeMdeO]

Hello @acassis , I can't understand pipeline issue, can you help me, please?

[acassis]

@FelipeMdeO I think you need to normalize this config:
boards/arm/ht32f491x3/esk32/configs/pwm/defconfig

More info: https://nuttx.apache.org/docs/latest/components/tools/refresh.html

@simbit18 could you please take a look too?

The CI is not clear what the issue is