Most major modes call that function.
If it is a name and no buffer by that name exists, create one and return it. Also, make sure the buffer is initialized with attributes necessary for use as a secondary process buffer, e.g. a marker delimiting the end of process output and the beginning of current user input. This function does not associate a secondary buffer with a primary process. SYMn buffer-local in the current buffer. If any variable is already buffer-local, don't do anything further to it.