The PCF8591 is plainly impossible to detect! Thus the driver won't even
try. You have to explicitly instantiate the device at the relevant
address (in the interval [0x48..0x4f]) either through platform data, or
-using the sysfs interface. See Documentation/i2c/instantiating-devices
+using the sysfs interface. See Documentation/i2c/instantiating-devices.rst
for details.
Directories are being created for each instantiated PCF8591: