I'm not aware of a particular term for the technique. What requires a single setup on one machine can require many setups on another machine, for many reasons other than the size of your work envelope. So it's really just "using multiple setups", regardless the reason.
It can be as hard or as easy as you make it. With good fixturing it is a reasonable technique for mass production, with poor foresight you could really waste a lot of time on even a single part. The key is to always bear in mind that you need a good reference point/edge/plane that can be positively located during both setups, so you can use it to fix all 3 axes before and after the move. Finding the reference can be done with fixturing, a dial, an edge finder... the list goes on. Sometimes it may be worthwhile to create a temporary reference during one setup that can be used as a reference to locate, but is then milled away during, the second setup.
Anything that can be said generally about machining a part in multiple setups applies to the case of a part that doesn't fit in your work envelope. I'd say it's the single most important, interesting, and challenging part of machining, period.