Unfamiliar C syntax in HLIST_HEAD_INIT

[Eric <eylin2004@xxxxxxxxx>]

While reading the kernel source, I noticed this macro:

#define HLIST_HEAD_INIT { .first = NULL } 

Which is used to initialize the struct: 

struct hlist_head { 

      struct hlist_node *first; 

}; 

My question is, what is the dot notation in ".first"?  I've never seen it before and couldn't find it in any C programming book I have on hand.  Couldn't this line just as easily be written as

#define HLIST_HEAD_INIT { NULL } 

? 

Thanks, 

Eric