NewcamD supports the reading of a card from a device connected to the serial port.
There's also (IIRC) a parm or three in the config file for the cardserver app. (which is an integral part of NewcamD) to enable/disable/configure it. Also a parm in Enigma to disable the serial port at boot? I think the latter is available on an Enigma menu, maybe Expert Settings.
slot0 is the serial port, slot1 the top reader, and slot2 the bottom reader - or something like that.
It's quite normal to use a Phoenix programmer to support this function (on a PC too) although I've never done it myself.
Read the cardserv config file readme section, or check my guide in the IG for more.