rtc: add driver for RX6110SA real time clock

The RX6110 comes in two different variants: SPI and I2C.
This driver only supports the SPI variant.

If the need ever arises to also support the I2C variant, this driver
could easily be refactored to support both cases.
Reviewed-by: Philipp Zabel <p.zabel@pengutronix.de>
Signed-off-by: Steffen Trumtrar <s.trumtrar@pengutronix.de>
Signed-off-by: Alexandre Belloni <alexandre.belloni@free-electrons.com>

drivers/rtc/Kconfig

@@ -743,6 +743,15 @@ config RTC_DRV_RX4581
 	  This driver can also be built as a module. If so the module
 	  will be called rtc-rx4581.
 
+config RTC_DRV_RX6110
+	tristate "Epson RX-6110"
+	select REGMAP_SPI
+	help
+	  If you say yes here you will get support for the Epson RX-6610.
+
+	  This driver can also be built as a module. If so the module
+	  will be called rtc-rx6110.
+
 config RTC_DRV_MCP795
 	tristate "Microchip MCP795"
 	help

drivers/rtc/Makefile

@@ -127,6 +127,7 @@ obj-$(CONFIG_RTC_DRV_RS5C372)	+= rtc-rs5c372.o
 obj-$(CONFIG_RTC_DRV_RV3029C2)	+= rtc-rv3029c2.o
 obj-$(CONFIG_RTC_DRV_RV8803)	+= rtc-rv8803.o
 obj-$(CONFIG_RTC_DRV_RX4581)	+= rtc-rx4581.o
+obj-$(CONFIG_RTC_DRV_RX6110)	+= rtc-rx6110.o
 obj-$(CONFIG_RTC_DRV_RX8010)	+= rtc-rx8010.o
 obj-$(CONFIG_RTC_DRV_RX8025)	+= rtc-rx8025.o
 obj-$(CONFIG_RTC_DRV_RX8581)	+= rtc-rx8581.o