/etc/inittab:
s0:2345:respawn:/sbin/agetty -L -h 115200 ttyUSB0 vt510

Tweaks to GNU screen to make it not start a login shell in every window:
/etc/screenrc: comment out "shell -$SHELL" 
~/.screenrc: deflogin off
~/.screenrc.vt510:
defflow on
defencoding UTF-8
deflogin off

To automatically resize to the remote terminal size:
/etc/profile.d/serial-resize.sh:
################################
# Not bash or zsh?
[ -n "${BASH_VERSION:-}" -o -n "${ZSH_VERSION:-}" ] || return 0

# Not an interactive shell?
[[ $- == *i* ]] || return 0

res() {

  old="$(stty -g)"
  stty raw -echo min 0 time 5

  printf '\0337\033[r\033[999;999H\033[6n\0338' > /dev/tty
  IFS='[;R' read -r _ rows cols _ < /dev/tty

  stty "$old"

  # echo "cols:$cols"
  # echo "rows:$rows"
  stty cols "$cols" rows "$rows"
}

res2() {

  old="$(stty -g)"
  stty raw -echo min 0 time 5

  printf '\033[18t' > /dev/tty
  IFS=';t' read -r _ rows cols _ < /dev/tty

  stty "$old"

  # echo "cols:$cols"
  # echo "rows:$rows"
  stty cols "$cols" rows "$rows"
}

[[ "$(tty)" == /dev/ttyUSB* ]] && res

return 0
###############################

To translate UTF-8 to ISO8859-1 and automatically start screen when logged in:
~/.profile:
########### at the end of the file
if [[ "$(tty)" == /dev/ttyUSB* ]]; then
        stty -iutf8
        export LANG=en_US
        export MANOPT="-E ascii"
        #exec screen -c ~/.screenrc.vt510
fi
###########