Only a Samsung engineer could tell you with certainty, and their employer would most likely prohibit it due to the proprietary nature.
In general, undocumented interfaces like that on circuit boards are used for development and acceptance testing purposes. They usually consist of a JTAG or other sort of in circuit programming/debugging interface. It's used to program the firmware and unique serial numbers at manufacture time, as well as to test for proper soldering and electrical functionality. There may also be a serial terminal interface for viewing boot and other log messages for troubleshooting and development purposes.
Sometimes engineers put extra connections purely for prototyping purposes. They want to be able to experiment on a new part or something, but PCBs are expensive to produce, so they will build flexibility into the board. Because they don't want to redo layout and everything, those vestigial connections might remain on the board even though the experiment has concluded.