Own serial driver for logon

We have written a device (/dev/ser3) for using for logon.
If we boot the system using /dev/ser1 we have access like normales, but to then use ‘new’ device we “reopen /dev/ser3”
The /dev/ser3 TeraTerm window then shows # sign, but /dev/ser1 still outputs the debug info from the ‘new’ device code.
(We can not type in /dev/ser1 TeraTerm.)
Typing in /dev/ser3 TeraTerm window, we get no reaction except for the debug info which shows that the /dev/ser3 data is being collected ready for a read() instruction.
please who calls read), how many time and why still stdout on /dev/ser1

Post your build file.