Thank you Alain,
udev rule fixed the serial interface port assignment problem
but this was not my real problem, from beginning I was aware that port name is changing when replugged.

The problem is OnSTep/Indiserver can not handshake but can talk :-)
not only occuring on UbuntuMate, I reproduced the same situation on Raspbian/Jessie
Now, my solution is power off and power on the OnStep hardware just after connecting from indiControl panel :-)
By doing this I am disabling the handshaink process I think.

I will test this by changing check_lx200_connection(int in_fd) function