this is a famous question in English dialect studies,Steep
verb
- to soak in water or other liquid, as to soften, cleanse, or extract some constituent: to steep tea in boiling-hot water; to steep reeds for basket weaving.
brew, mash, mask, steep, stew are all used for infusing tea in different areas,
there's certainly a map in the English Dialect Survey but I can't find it on the internet.