pwm: add Rockchip SoC PWM support

This commit adds a driver for the PWM controller found on Rockchip
RK29, RK30 and RK31 SoCs.

Signed-off-by: Beniamino Galvani <b.galvani@gmail.com>
Signed-off-by: Thierry Reding <thierry.reding@gmail.com>
diff --git a/drivers/pwm/Kconfig b/drivers/pwm/Kconfig
index 4ad7b89..a86879a 100644
--- a/drivers/pwm/Kconfig
+++ b/drivers/pwm/Kconfig
@@ -206,6 +206,13 @@
 	  To compile this driver as a module, choose M here: the module
 	  will be called pwm-renesas-tpu.
 
+config PWM_ROCKCHIP
+	tristate "Rockchip PWM support"
+	depends on ARCH_ROCKCHIP
+	help
+	  Generic PWM framework driver for the PWM controller found on
+	  Rockchip SoCs.
+
 config PWM_SAMSUNG
 	tristate "Samsung PWM support"
 	depends on PLAT_SAMSUNG