Confirming that the below itinerary will apply as I have heard conflicting advice on the need for "interline" tickets:

LAX >> PVG >> LAX (Airline A)
Within the above round trip I have a
PVG >> ICN >> PVG (Airline B)

What I have gathered here is that I can treat the two flights above as the following trips but will want to print out separate itineraries for each leg:
LAX>>PVG>>ICN
ICN>>PVG>>LAX