How to make use of an M2 PCIe card UART interface?

I have a motherboard (AIMB-218) with an M2 E key slot and according to the documentation of the said motherboard the M2 slot supports UART. I am trying to use a wireless module (Wi-Fi + Bluetooth), which has a UART interface for controlling the Bluetooth adapter. Its documentation says that the Wi-Fi interface works using the PCIe bus and the Bluetooth uses UART interface. I have booted a Linux Ubuntu on this system, but the UART interface does not show up in the /dev folder (there are only few ttyS* entries which correspond to serial ports present on the motherboard) nor the Bluetooth controller appears in the system in any other way - the bluetoothctl does not list any HCI devices. The wireless module's chip is 88W8997 and the manufacturer claims it is supported by the Linux kernel. My question is: How to make use of the UART interface of the card connected to the M2 slot?