Going through the template writing Wiki, I noticed that there was a helper method to create serial console entries for PXELinux templates.

http://projects.theforeman.org/projects/foreman/wiki/TemplateWriting#Functions-and-macros

Upon trying to actually use the method, I couldn't figure out how it worked.

After asking in #theforeman in IRC, Ohad eventually responded with:

22:56 <ohadlevy> it was a very old leftover, probably needs picking up fixing, mind creating an issue?

Either this helper needs to be better documented, or 'cleaned up' since its apparently old.