scripts: kernel-doc: improve nested logic to handle multiple identifiers

scripts: kernel-doc: improve nested logic to handle multiple identifiers

It is possible to use nested structs like:

struct {
	struct {
		void *arg1;
	} st1, st2, *st3, st4;
};

Handling it requires to split each parameter. Change the logic
to allow such definitions.

In order to test the new nested logic, the following file
was used to test

<code>
struct foo { int a; }; /* Just to avoid errors if compiled */

/**
 * struct my_struct - a struct with nested unions and structs
 * @arg1: first argument of anonymous union/anonymous struct
 * @arg2: second argument of anonymous union/anonymous struct
 * @arg1b: first argument of anonymous union/anonymous struct
 * @arg2b: second argument of anonymous union/anonymous struct
 * @arg3: third argument of anonymous union/anonymous struct
 * @arg4: fourth argument of anonymous union/anonymous struct
 * @bar.st1.arg1: first argument of struct st1 on union bar
 * @bar.st1.arg2: second argument of struct st1 on union bar
 * @bar.st1.bar1: bar1 at st1
 * @bar.st1.bar2: bar2 at st1
 * @bar.st2.arg1: first argument of struct st2 on union bar
 * @bar.st2.arg2: second argument of struct st2 on union bar
 * @bar.st3.arg2: second argument of struct st3 on union bar
 * @f1: nested function on anonimous union/struct
 * @bar.st2.f2: nested function on named union/struct
 */
struct my_struct {
   /* Anonymous union/struct*/
   union {
	struct {
	    char arg1 : 1;
	    char arg2 : 3;
	};
       struct {
           int arg1b;
           int arg2b;
       };
       struct {
           void *arg3;
           int arg4;
           int (*f1)(char foo, int bar);
       };
   };
   union {
       struct {
           int arg1;
           int arg2;
	   struct foo bar1, *bar2;
       } st1;           /* bar.st1 is undocumented, cause a warning */
       struct {
           void *arg1;  /* bar.st3.arg1 is undocumented, cause a warning */
	    int arg2;
          int (*f2)(char foo, int bar); /* bar.st3.fn2 is undocumented, cause a warning */
       } st2, st3, *st4;
       int (*f3)(char foo, int bar); /* f3 is undocumented, cause a warning */
   } bar;               /* bar is undocumented, cause a warning */

   /* private: */
   int undoc_privat;    /* is undocumented but private, no warning */

   /* public: */
   int undoc_public;    /* is undocumented, cause a warning */
};
</code>

It produces the following warnings, as expected:

test2.h:57: warning: Function parameter or member 'bar' not described in 'my_struct'
test2.h:57: warning: Function parameter or member 'bar.st1' not described in 'my_struct'
test2.h:57: warning: Function parameter or member 'bar.st2' not described in 'my_struct'
test2.h:57: warning: Function parameter or member 'bar.st3' not described in 'my_struct'
test2.h:57: warning: Function parameter or member 'bar.st3.arg1' not described in 'my_struct'
test2.h:57: warning: Function parameter or member 'bar.st3.f2' not described in 'my_struct'
test2.h:57: warning: Function parameter or member 'bar.st4' not described in 'my_struct'
test2.h:57: warning: Function parameter or member 'bar.st4.arg1' not described in 'my_struct'
test2.h:57: warning: Function parameter or member 'bar.st4.arg2' not described in 'my_struct'
test2.h:57: warning: Function parameter or member 'bar.st4.f2' not described in 'my_struct'
test2.h:57: warning: Function parameter or member 'bar.f3' not described in 'my_struct'
test2.h:57: warning: Function parameter or member 'undoc_public' not described in 'my_struct'

Suggested-by: Markus Heiser <markus.heiser@darmarit.de>
Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>
Signed-off-by: Jonathan Corbet <corbet@lwn.net>