#/lib/udev/rules.d/50-udev-default.rules:SUBSYSTEM=="rtc", ATTR{hctosys}=="1", SYMLINK+="rtc"
#/lib/udev/rules.d/50-udev-default.rules:SUBSYSTEM=="rtc", KERNEL=="rtc0", SYMLINK+="rtc", OPTIONS+="link_priority=-100"

# I2C RTC, when added and not the source of the sys clock (kernel), is used ;
# separate name to ensure rtc-i2c.service will not be run on anything else
ACTION=="add", SUBSYSTEMS=="i2c", SUBSYSTEM=="rtc", KERNEL=="rtc0", ATTR{hctosys}=="0", SYMLINK+="rtc_i2c", TAG+="systemd"