As far as "a place putting this down formally," see the AMS's 2004 "Information Statement on Joint Research and its Publication" at http://www.ams.org/profession/leaders/culture/culturehttp://www.ams.org/profession/leaders/culture/CultureStatement04.pdf.
The AMS has several of these "culture statements," intended to "highlight the ways in which the traditions in mathematics differ from those in other disciplines." I.e. to convince the skeptical dean that you really deserve that promotion.