The old /dev/rtc used node (10,135), the new rtc core has changed to allow dynamic allocation. As the new core allows more than one individual RTC, you may end up with /dev/rtc0, /dev/rtc1.
The new format for the module names of RTC drivers is rtc-*, so the old s3c2410_rtc has been renamed rtc-s3c. You will need to update your module loader configuration to take note of this if you build a modular driver.