Search notes:

/dev/rtcN

While /dev/rtc reports real time clock signals for ACPI and PC - Personal Computer platforms, /dev/rtcN (where N is a number) supports other real time clock models.

See also

/sys/class/rtc/rtcN, /dev/rtc
This interface seems to be testable with tools/teting/selftests/timers/rtctest.c.

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