This is the user documentation for the flink userspace library in C. It provides a device and bus independent interface to the underlying driver modules. For more information about the inner workings see flink Userspace Library on Github. The API of the library can be found under API
Here, the subdevice with unique_id = 0x23a5 is selected. This has the advantage that this unique_id does not change even in the case where subdevices are arranged differently in a FPGA design.
Now you can communicate with this selected subdevice. Assuming that it's of type GPIO you could configure it as an input or output.