rtc: add Dallas DS1390/93/94 RTC chips

Add support for the Dallas DS1390/93/94 SPI RTC chip.

Signed-off-by: Mark Jackson <mpfj@mimc.co.uk>
Acked-by: Alessandro Zummo <a.zummo@towertech.it>
Cc: David Brownell <david-b@pacbell.net>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

drivers/rtc/Kconfig

@@ -310,6 +310,17 @@ config RTC_DRV_DS1305
 	  This driver can also be built as a module. If so, the module
 	  will be called rtc-ds1305.
 
+config RTC_DRV_DS1390
+	tristate "Dallas/Maxim DS1390/93/94"
+	help
+	  If you say yes here you get support for the DS1390/93/94 chips.
+
+	  This driver only supports the RTC feature, and not other chip
+	  features such as alarms and trickle charging.
+
+	  This driver can also be built as a module. If so, the module
+	  will be called rtc-ds1390.
+
 config RTC_DRV_MAX6902
 	tristate "Maxim MAX6902"
 	help