Couldn't register serial port 0000:02:0a.2: -28

I run into a problem where I have a device which has two normal serial ports and some on a PCI device. After booting the kernel I got this error line:

Couldn’t register serial port 0000:02:0a.2: -28

In order to get more than 2 serial ports working, I “fixed” my currently used kernel config:

CONFIG_SERIAL_8250_NR_UARTS=32 CONFIG_SERIAL_8250_RUNTIME_UARTS=6