docs/vm: add index.rst and link MM documentation to top level index

Signed-off-by: Mike Rapoport <rppt@linux.vnet.ibm.com>
Signed-off-by: Jonathan Corbet <corbet@lwn.net>

Documentation/index.rst

@@ -89,6 +89,7 @@ needed).
    sound/index
    crypto/index
    filesystems/index
+   vm/index
 
 Architecture-specific documentation
 -----------------------------------

Documentation/vm/conf.py

+# -*- coding: utf-8; mode: python -*-
+
+project = "Linux Memory Management Documentation"
+
+tags.add("subproject")
+
+latex_documents = [
+    ('index', 'memory-management.tex', project,
+     'The kernel development community', 'manual'),
+]

Documentation/vm/index.rst

+=====================================
+Linux Memory Management Documentation
+=====================================
+
+This is a collection of documents about Linux memory management (mm) subsystem.
+
+User guides for MM features
+===========================
+
+The following documents provide guides for controlling and tuning
+various features of the Linux memory management
+
+.. toctree::
+   :maxdepth: 1
+
+   hugetlbpage
+   idle_page_tracking
+   ksm
+   numa_memory_policy
+   pagemap
+   transhuge
+   soft-dirty
+   swap_numa
+   userfaultfd
+   zswap
+
+Kernel developers MM documentation
+==================================
+
+The below documents describe MM internals with different level of
+details ranging from notes and mailing list responses to elaborate
+descriptions of data structures and algorithms.
+
+.. toctree::
+   :maxdepth: 1
+
+   active_mm
+   balance
+   cleancache
+   frontswap
+   highmem
+   hmm
+   hwpoison
+   hugetlbfs_reserv
+   mmu_notifier
+   numa
+   overcommit-accounting
+   page_migration
+   page_frags
+   page_owner
+   remap_file_pages
+   slub
+   split_page_table_lock
+   unevictable-lru
+   z3fold
+   zsmalloc