Override file in FreeSWITCH config template directory. Each top-level attribute denotes a file path in the configuration directory, its value is the file path. See FreeSWITCH documentation for more info. Also check available templates in FreeSWITCH repository.

{ }

{
  "freeswitch.xml" = ./freeswitch.xml;
  "dialplan/default.xml" = pkgs.writeText "dialplan-default.xml" ''
    [xml lines]
  '';
}