checkdoc-style-hooks is a variable defined in `checkdoc.el'.
Its value is

Hook run after the standard style check is completed.
All functions must return nil or a string representing the error found.
Useful for adding new user implemented commands.

Each hook is called with two parameters, (DEFUNINFO ENDPOINT).
DEFUNINFO is the return value of `checkdoc-defun-info'. ENDPOINT is the
location of end of the documentation string.