When I was at university (in the UK) as a lecturer we adopted the following scheme: We made students aware that if they have any disabilities they wish us to consider (dyslexia, mental health, physical disabilities,...) that affected their studies, they should let the university office know. The office (after confirming the disability) then let the students home school aware. The needs (for example special arrangements for course work, exams) were then relayed with the minimum of information to the schools disability officer (this was a lecturer who had no background knowledge of any particular disability and was a pure admin role) who passed the information on to the staff taking the modules the students were enrolled on.
Your supervisor will presumably be told of any special circumstances you require that he can be of assistance with.
It isn't obvious is this approach is adopted country-wide, though all institutions have to comply the Disability Discrimination Act.