The Z8530 driver is written to be portable. In DMA mode it makes assumptions about the use of ISA DMA. These are probably warranted in most cases as the Z85230 in paticular was designed to glue to PC type machines. The PIO mode makes no real assumptions.
Should you need to retarget the Z8530 driver to another architecture the only code that should need changing are the port I/O functions. At the moment these assume PC I/O port accesses. This may not be appropriate for all platforms. Replacing z8530_read_port and z8530_write_port is intended to be all that is required to port this driver layer.