What is "#define alloc_ieee80211 alloc_ieee80211_rsl"?

[John Whitmore]

Sorry I know what a #define is doing, but in this case I've no idea
why it's used and what it's trying to achieve.

This is from the rtl8192u driver in staging, where the alloc function
(alloc_ieee80211) which is called by the probe function
(rtl8192_usb_probe). So that's all good but a quick grep through the
code and in the file drivers/staging/rtl8192u/ieee80211/ieee80211.h
there's a line which defines that function as another function '_rsl'
which don't exist anywhere in Kernel.

#define alloc_ieee80211			alloc_ieee80211_rsl

So what am I missing or why are a number of functions being redefined
as another name, which doesn't exist?

I'm tempted to remove any that don't exist but I should really find
out what it is the lines are doing.