Booting from external SD Card with a Jetson Nano(16gb emmc)

Hi, I’m trying to boot with my Jetson Nano((16gb emmc)) and a customised carrier board from the external SDCARD , I can’t find a detailed method, has anyone made it happen?

ps: The office jetson nano OS can’t recognize the external SDCARD.

Could you provide more detail information.(e.g: log , dts , layout file)