Jetson board has both I2C and SPI ROM assembled. Are those alternative methods for storing the ID data or what’s the reason of having both there?

I2C ROM is for board ID, SPI flash is for SPI boot mode which is different to eMMC boot mode.

Thanks for the reply. What’s the ID data on EEPROM? Is this EEPROM mandatory for the custom HW or can this data be stored on EMMC etc mass storage? Is there more information available on some document?

The EEPROM is not mandatory, Development board use the ID data to identify different board configuration.
You can uncomment the board-id in the jetson-tk1.conf file.
The SPI ROM is also not mandatory if you use EMMC for store U-Boot.