[ 0.590705] 00:08: ttyS0 at I/O 0x3f8 (irq = 4, base_baud = 115200) is a 16550A
The line above tell us that the kernel detected a 16550 UART chip in your PC, which provides a serial port (ttyS0), and there's some resources allocated to it (0x3f8 I/O address, IRQ 4).
The default permissions for serial devices are the following:
crw-rw---- 1 root dialout ... /dev/ttyS0
So, if you are a member of the
dialout group, you'll be able to access (read from/write to) the serial port devices. Add yourself to the
dialout group by running:
sudo adduser $USER dialout
sudo adduser <username> dialout
Then log out and log in again. Now you should have access to the serial port. Of course, you must also input the correct settings (speed, data bits, parity, stop bits, flow control) in the program you're using to access the device.