bpf, docs: Fix ordering of bpf documentation

This commit fixes the display of the BPF documentation in the sidebar
when rendered as HTML.

Before this patch, the sidebar would render as follows for some
sections:

| BPF Documentation
  |- BPF Type Format (BTF)
    |- BPF Type Format (BTF)

This was due to creating a heading in index.rst followed by
a sphinx toctree, where the file referenced carries the same
title as the section heading.

To fix this I applied a pattern that has been established in other
subfolders of Documentation:

1. Re-wrote index.rst to have a single toctree
2. Split the sections out in to their own files

Additionally maps.rst and programs.rst make use of a glob pattern to
include map_* or prog_* rst files in their toctree, meaning future map
or program type documentation will be automatically included.

Signed-off-by: Dave Tucker <dave@dtucker.co.uk>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Link: https://lore.kernel.org/bpf/1a1eed800e7b9dc13b458de113a489641519b0cc.1636749493.git.dave@dtucker.co.uk

Documentation/bpf/faq.rst

@@ -0,0 +1,11 @@
+================================
+Frequently asked questions (FAQ)
+================================
+
+Two sets of Questions and Answers (Q&A) are maintained.
+
+.. toctree::
+   :maxdepth: 1
+
+   bpf_design_QA
+   bpf_devel_QA

Documentation/bpf/helpers.rst

@@ -0,0 +1,7 @@
+Helper functions
+================
+
+* `bpf-helpers(7)`_ maintains a list of helpers available to eBPF programs.
+
+.. Links
+.. _bpf-helpers(7): https://man7.org/linux/man-pages/man7/bpf-helpers.7.html

Documentation/bpf/index.rst

@@ -12,97 +12,26 @@ BPF instruction-set.
 The Cilium project also maintains a `BPF and XDP Reference Guide`_
 that goes into great technical depth about the BPF Architecture.
 
-libbpf
-======
-
-Documentation/bpf/libbpf/libbpf.rst is a userspace library for loading and interacting with bpf programs.
-
-BPF Type Format (BTF)
-=====================
-
 .. toctree::
    :maxdepth: 1
 
+   libbpf/index
    btf
-
-
-Frequently asked questions (FAQ)
-================================
-
-Two sets of Questions and Answers (Q&A) are maintained.
-
-.. toctree::
-   :maxdepth: 1
-
-   bpf_design_QA
-   bpf_devel_QA
-
-Syscall API
-===========
-
-The primary info for the bpf syscall is available in the `man-pages`_
-for `bpf(2)`_. For more information about the userspace API, see
-Documentation/userspace-api/ebpf/index.rst.
-
-Helper functions
-================
-
-* `bpf-helpers(7)`_ maintains a list of helpers available to eBPF programs.
-
-
-Program types
-=============
-
-.. toctree::
-   :maxdepth: 1
-
-   prog_cgroup_sockopt
-   prog_cgroup_sysctl
-   prog_flow_dissector
-   bpf_lsm
-   prog_sk_lookup
-
-
-Map types
-=========
-
-.. toctree::
-   :maxdepth: 1
-
-   map_cgroup_storage
-
-
-Testing and debugging BPF
-=========================
-
-.. toctree::
-   :maxdepth: 1
-
-   drgn
-   s390
-
-
-Licensing
-=========
-
-.. toctree::
-   :maxdepth: 1
-
+   faq
+   syscall_api
+   helpers
+   programs
+   maps
    bpf_licensing
+   test_debug
+   other
 
+.. only::  subproject and html
 
-Other
-=====
+   Indices
+   =======
 
-.. toctree::
-   :maxdepth: 1
-
-   ringbuf
-   llvm_reloc
+   * :ref:`genindex`
 
 .. Links:
-.. _networking-filter: ../networking/filter.rst
-.. _man-pages: https://www.kernel.org/doc/man-pages/
-.. _bpf(2): https://man7.org/linux/man-pages/man2/bpf.2.html
-.. _bpf-helpers(7): https://man7.org/linux/man-pages/man7/bpf-helpers.7.html
 .. _BPF and XDP Reference Guide: https://docs.cilium.io/en/latest/bpf/

Documentation/bpf/libbpf/index.rst

@@ -3,8 +3,6 @@
 libbpf
 ======
 
-For API documentation see the `versioned API documentation site <https://libbpf.readthedocs.io/en/latest/api.html>`_.
-
 .. toctree::
    :maxdepth: 1
 
@@ -14,6 +12,8 @@ For API documentation see the `versioned API documentation site <https://libbpf.
 This is documentation for libbpf, a userspace library for loading and
 interacting with bpf programs.
 
+For API documentation see the `versioned API documentation site <https://libbpf.readthedocs.io/en/latest/api.html>`_.
+
 All general BPF questions, including kernel functionality, libbpf APIs and
 their application, should be sent to bpf@vger.kernel.org mailing list.
 You can `subscribe <http://vger.kernel.org/vger-lists.html#bpf>`_ to the

Documentation/bpf/maps.rst

@@ -0,0 +1,9 @@
+=========
+Map Types
+=========
+
+.. toctree::
+   :maxdepth: 1
+   :glob:
+
+   map_*

Documentation/bpf/other.rst

@@ -0,0 +1,9 @@
+=====
+Other
+=====
+
+.. toctree::
+   :maxdepth: 1
+
+   ringbuf
+   llvm_reloc

Documentation/bpf/programs.rst

@@ -0,0 +1,9 @@
+=============
+Program Types
+=============
+
+.. toctree::
+   :maxdepth: 1
+   :glob:
+
+   prog_*

Documentation/bpf/syscall_api.rst

@@ -0,0 +1,11 @@
+===========
+Syscall API
+===========
+
+The primary info for the bpf syscall is available in the `man-pages`_
+for `bpf(2)`_. For more information about the userspace API, see
+Documentation/userspace-api/ebpf/index.rst.
+
+.. Links:
+.. _man-pages: https://www.kernel.org/doc/man-pages/
+.. _bpf(2): https://man7.org/linux/man-pages/man2/bpf.2.html

Documentation/bpf/test_debug.rst

@@ -0,0 +1,9 @@
+=========================
+Testing and debugging BPF
+=========================
+
+.. toctree::
+   :maxdepth: 1
+
+   drgn
+   s390