I don't think there is a specific name for it, any more than there is for playing on the higher keys of a piano. It's just making use of the full range of the guitar. To many people, the upper reaches of the fingerboard is terra incognita (Here Be Dragons). The nice people who make guitars put it there for you to use, whether you chose to or not.

(If guitars were pianos, most people would use only the left side)

Don Firth