The C-Rio only allows for 1 extra Ethernet cable other than the one for the wireless bridge.
The wireless bridge plugs in to the Ethernet port #1 on the Crio.
The KOP camera plugs directly into the Ethernet port #2 on the Crio.
I dont think you can plug another camera in to the Crio unless you do as other posts have mentioned and use a small laptop on the robot.
I searched the manual for camera rules and all i could find were:
"The chassis for the cRIO-FRC and the supplied KOP camera have grounded
enclosures. Under this rule (and for their protection), it is required that they be
electrically isolated from the ROBOT frame when installed on the ROBOT."
and
"<R64> Any decorations that involve broadcasting a signal to/from the ROBOT, such as remote
cameras, must be cleared with FIRST Engineering (via e-mail to
frcteams@usfirst.org) prior
to the event and tested for communications interference at the venue. Such devices, if
reviewed and approved, are excluded from Rule <R52>."
I would take your question to the FRC Q&A, check the Posts there to see if anyone has already asked this question.