OK, I'm a Flambeau. Why should I revere this place that shows up so often?
Doisstep was a large covenant in the "Prvoencial Tribunal" when white wolf and lion rampanthad the game. It shows up in detail in the 1990 covenants book and in the adventure "a midsummer night's dream" a bit later.
It hasn't shown up in published ars material since white wolf sold the game to Wizards, the covenant of Doisstep did become a very big deal in Mage the Ascension.
Atlas does have the rights to use the name but I doubt that they will ever use them. One plot concerned with it was that Doisstep was going to become the new domus magnus of house flambeau now that val negra was sinking into winter. Another is that Doisstep was also the home of a pre-mysteries incarnation of the cult of mercury.
As pointed out by lojosang on another thread, Doissetep did appear in the original Houses of Hermes supplement, published by Wizards. I haven't got that book handy, but IIRC it was implied that Val-Negra had slipped so far into winter that by 1220 the primus of Flambeau opted to live at Doissetep instead.
In the real world Doissetep is a major Buddhist monastery in Thailand. I guess the name sounded cool to the WW boys.