WDR-4900 v1 - what are JP1 and JP3 used for?

hello,

on hardware page for TP-link WDR-4900 v1 there is a photo for serial pinouts (JP2):

the board also has another JP1 (2x8pins) and JP3 (1x4pins, upper left corner).
what are these pinouts used for?

thank you,
geos

JP1 is jtag for the main cpu