lib min_heap: add brief introduction to Min Heap API

A short description of the Min Heap API is added to the min_heap.h,
explaining its purpose for managing min-heaps and emphasizing the use of
macro wrappers instead of direct function calls.  For more details, users
are directed to the documentation at Documentation/core-api/min_heap.rst.

Link: https://lkml.kernel.org/r/20241129181222.646855-4-visitorckw@gmail.com
Signed-off-by: Kuan-Wei Chiu <visitorckw@gmail.com>
Cc: Ching-Chun (Jim) Huang <jserv@ccns.ncku.edu.tw>
Cc: Geert Uytterhoeven <geert@linux-m68k.org>
Cc: Jonathan Corbet <corbet@lwn.net>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

include/linux/min_heap.h

@@ -6,6 +6,17 @@
 #include <linux/string.h>
 #include <linux/types.h>
 
+/*
+ * The Min Heap API provides utilities for managing min-heaps, a binary tree
+ * structure where each node's value is less than or equal to its children's
+ * values, ensuring the smallest element is at the root.
+ *
+ * Users should avoid directly calling functions prefixed with __min_heap_*().
+ * Instead, use the provided macro wrappers.
+ *
+ * For further details and examples, refer to Documentation/core-api/min_heap.rst.
+ */
+
 /**
  * Data structure to hold a min-heap.
  * @nr: Number of elements currently in the heap.