i have a question:
how to disable serial port input temporarily?
except disconnect TX wire
I've not tried to do that before, however it should be as easy as changing the kernel command line variable in uBoot to point to an unused tty.
If you want to remove serial access to uBoot as well, that would require editing the uboot code and reflashing and would present real risk of it being permanent.
dont remove, only disable input and keep log output
Ok, I’m not sure how to do this in openwrt, but in Desktop Linux you would remove / disable the getty instance for the console tty.
This will be started in one of the init scripts.