coding-system-eol-type is a built-in function in `C source code'.

(coding-system-eol-type CODING-SYSTEM)

Return eol-type of CODING-SYSTEM.
An eol-type is an integer 0, 1, 2, or a vector of coding systems.

Integer values 0, 1, and 2 indicate a format of end-of-line; LF, CRLF,
and CR respectively.

A vector value indicates that a format of end-of-line should be
detected automatically. Nth element of the vector is the subsidiary
coding system whose eol-type is N.