I2C Real-Time Clock
0x68 (fixed)
Register device:
echo ds1307 0x68 > /sys/bus/i2c/devices/i2c-<port+2>/new_device
Finding device class node:
for chip in $(find /sys/class/rtc -name rtc*)
do
if [[ "$(cat $chip/name)" == "ds1307" ]]
then
# do whatever
fi
done