This setting enable Saleculator support more than 4 serial devices

Ctrl+Alt+F1
1. Type below command to edit file /etc/default/grub
nano /etc/default/grub
Set below value
GRUB_CMDLINE_LINUX=”8250.nr_uarts=8″

Now press CTRL+X, Y, Enter to save file

2. Type below command and press enter
update-grub

3. Reboot