I would appreciate if somebody can be more specific, how this can be
done. I am using the defaults for syslog, which came with Fedora 21
x86_64.

Kevin, I understand your frustration.  I think I used the wrong term.
It's not a "log level" thing, but a "dynamic debug" thing.  Dynamic 
Debug lets you turn on your specific message without seeing all other 
messages of the same "level."  But that means you may have to explicitly 
turn it off.

See:

google://pr_info
http://lwn.net/Articles/487437/
https://lwn.net/Articles/434833/

 From the last link:

Turning on dynamic debug causes a new virtual file to appear at
/sys/kernel/debug/dynamic_debug/control (modulo any individual
preferences for the location of debugfs, naturally). Writing to that
file will enable or disable specific debugging functions, as
specified by a simple but flexible language.

echo file tpm_nsc.c function init_nsc +p > .../dynamic_debug/control

So your incantation would be something like:

echo file myfile.c function init_me -p > mypath/dynamic_debug/control

LWN has a dynamic debug howto.  I assume it's in kernel docs too.

-- 
Larry Martin
www.GlueLogix.com
Design, Test and Support of Computerized Systems
desk USA 919.342.0201
cell USA 919.641.1733