Comment 8 for bug 1810416

the above is on Dell Latitude 5490 with RTS525A card reader.

xubuntu@xubuntu:~$ lspci -v
[..]
01:00.0 Unassigned class [ff00]: Realtek Semiconductor Co., Ltd. RTS525A PCI Express Card Reader (rev 01)
 Subsystem: Dell RTS525A PCI Express Card Reader
 Flags: bus master, fast devsel, latency 0, IRQ 125
 Memory at ef100000 (32-bit, non-prefetchable) [size=4K]
 Capabilities: <access denied>
 Kernel driver in use: rtsx_pci
 Kernel modules: rtsx_pci

and the relevant "lshw" section:
           *-generic
                description: Unassigned class
                product: RTS525A PCI Express Card Reader
                vendor: Realtek Semiconductor Co., Ltd.
                physical id: 0
                bus info: pci@0000:01:00.0
                version: 01
                width: 32 bits
                clock: 33MHz
                capabilities: bus_master cap_list
                configuration: driver=rtsx_pci latency=0
                resources: irq:125 memory:ef100000-ef100fff