Prisma provides a baselining feature - that is, describing a database state before any Prisma migration was applied. It is done by providing an initial migration file, which serves as a baseline.

You can edit the initial migration to include schema elements that cannot be represented in the Prisma schema - such as stored procedures or triggers. However, there is a caveat - adding triggers or procedures which should refer to entities created in following Prisma migrations doesn't seem to be feasible that way.

Documentation link: Baselining a database