pwm: airoha: Add support for EN7581 SoC

Introduce driver for PWM module available on EN7581 SoC.

Limitations:
- Only 8 concurrent waveform generators are available for 8 combinations of
  duty_cycle and period. Waveform generators are shared between 16 GPIO
  pins and 17 SIPO GPIO pins.
- Supports only normal polarity.
- On configuration the currently running period is completed.
- Minimum supported period is 4 ms
- Maximum supported period is 1s

Signed-off-by: Benjamin Larsson <benjamin.larsson@genexis.eu>
Reviewed-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@collabora.com>
Co-developed-by: Lorenzo Bianconi <lorenzo@kernel.org>
Signed-off-by: Lorenzo Bianconi <lorenzo@kernel.org>
Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Co-developed-by: Christian Marangi <ansuelsmth@gmail.com>
Signed-off-by: Christian Marangi <ansuelsmth@gmail.com>
Link: https://patch.msgid.link/20251013103408.14724-1-ansuelsmth@gmail.com
Signed-off-by: Uwe Kleine-König <ukleinek@kernel.org>

drivers/pwm/Kconfig

@@ -63,6 +63,16 @@ config PWM_ADP5585
 	  This option enables support for the PWM function found in the Analog
 	  Devices ADP5585.
 
+config PWM_AIROHA
+	tristate "Airoha PWM support"
+	depends on ARCH_AIROHA || COMPILE_TEST
+	select REGMAP_MMIO
+	help
+	  Generic PWM framework driver for Airoha SoC.
+
+	  To compile this driver as a module, choose M here: the module
+	  will be called pwm-airoha.
+
 config PWM_APPLE
 	tristate "Apple SoC PWM support"
 	depends on ARCH_APPLE || COMPILE_TEST

drivers/pwm/Makefile

@@ -2,6 +2,7 @@
 obj-$(CONFIG_PWM)		+= core.o
 obj-$(CONFIG_PWM_AB8500)	+= pwm-ab8500.o
 obj-$(CONFIG_PWM_ADP5585)	+= pwm-adp5585.o
+obj-$(CONFIG_PWM_AIROHA)	+= pwm-airoha.o
 obj-$(CONFIG_PWM_APPLE)		+= pwm-apple.o
 obj-$(CONFIG_PWM_ARGON_FAN_HAT)	+= pwm-argon-fan-hat.o
 obj-$(CONFIG_PWM_ATMEL)		+= pwm-atmel.o