rtc: rv3028: add new driver

Add a driver for the MicroCrystal RV-3028. It is a SMT Real-Time Clock
Module that incorporates an integrated CMOS circuit together with an XTAL.
It has an i2c interface.

The driver handles date/time, alarms, trickle charging, timestamping,
frequency offset correction, EEPROM and NVRAM.
Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>

Documentation/devicetree/bindings/rtc/rtc.txt

@@ -52,6 +52,7 @@ emmicro,em3027		EM Microelectronic EM3027 Real-time Clock
 isil,isl1208		Intersil ISL1208 Low Power RTC with Battery Backed SRAM
 isil,isl1218		Intersil ISL1218 Low Power RTC with Battery Backed SRAM
 isil,isl12022		Intersil ISL12022 Real-time Clock
+microcrystal,rv3028	Real Time Clock Module with I2C-Bus
 microcrystal,rv3029	Real Time Clock Module with I2C-Bus
 microcrystal,rv8523	Real Time Clock
 nxp,pcf2127		Real-time clock

drivers/rtc/Kconfig

@@ -626,6 +626,15 @@ config RTC_DRV_EM3027
 	  This driver can also be built as a module. If so, the module
 	  will be called rtc-em3027.
 
+config RTC_DRV_RV3028
+	tristate "Micro Crystal RV3028"
+	help
+	  If you say yes here you get support for the Micro Crystal
+	  RV3028.
+
+	  This driver can also be built as a module. If so, the module
+	  will be called rtc-rv3028.
+
 config RTC_DRV_RV8803
 	tristate "Micro Crystal RV8803, Epson RX8900"
 	help

drivers/rtc/Makefile

@@ -139,6 +139,7 @@ obj-$(CONFIG_RTC_DRV_RS5C313)	+= rtc-rs5c313.o
 obj-$(CONFIG_RTC_DRV_RS5C348)	+= rtc-rs5c348.o
 obj-$(CONFIG_RTC_DRV_RS5C372)	+= rtc-rs5c372.o
 obj-$(CONFIG_RTC_DRV_RTD119X)	+= rtc-rtd119x.o
+obj-$(CONFIG_RTC_DRV_RV3028)	+= rtc-rv3028.o
 obj-$(CONFIG_RTC_DRV_RV3029C2)	+= rtc-rv3029c2.o
 obj-$(CONFIG_RTC_DRV_RV8803)	+= rtc-rv8803.o
 obj-$(CONFIG_RTC_DRV_RX4581)	+= rtc-rx4581.o