dm: reset: add stm32 reset driver

This driver is adapted from linux drivers/reset/reset-stm32.c
It's compatible with STM32 F4/F7/H7 SoCs.

This driver doesn't implement .of_match as it's binded
by MFD RCC driver.

To add support for each SoC family, a SoC's specific
include/dt-binfings/mfd/stm32xx-rcc.h file must be added.

This patch only includes stm32h7-rcc.h dedicated for STM32H7 SoCs.
Other SoCs support will be added in the future.

Signed-off-by: Patrice Chotard <patrice.chotard@st.com>
Reviewed-by: Simon Glass <sjg@chromium.org>
diff --git a/doc/device-tree-bindings/reset/st,stm32-rcc.txt b/doc/device-tree-bindings/reset/st,stm32-rcc.txt
new file mode 100644
index 0000000..01db343
--- /dev/null
+++ b/doc/device-tree-bindings/reset/st,stm32-rcc.txt
@@ -0,0 +1,6 @@
+STMicroelectronics STM32 Peripheral Reset Controller
+====================================================
+
+The RCC IP is both a reset and a clock controller.
+
+Please see Documentation/devicetree/bindings/clock/st,stm32-rcc.txt