bpf, docs: Split general purpose eBPF documentation out of filter.rst

filter.rst starts out documenting the classic BPF and then spills into
introducing and documentating eBPF.  Move the eBPF documentation into
rwo new files under Documentation/bpf/ for the instruction set and
the verifier and link to the BPF documentation from filter.rst.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: Song Liu <songliubraving@fb.com>
Link: https://lore.kernel.org/bpf/20211119163215.971383-6-hch@lst.de

Documentation/bpf/index.rst

@@ -5,16 +5,15 @@ BPF Documentation
 This directory contains documentation for the BPF (Berkeley Packet
 Filter) facility, with a focus on the extended BPF version (eBPF).
 
-This kernel side documentation is still work in progress. The main
-textual documentation is (for historical reasons) described in
-:ref:`networking-filter`, which describe both classical and extended
-BPF instruction-set.
+This kernel side documentation is still work in progress.
 The Cilium project also maintains a `BPF and XDP Reference Guide`_
 that goes into great technical depth about the BPF Architecture.
 
 .. toctree::
    :maxdepth: 1
 
+   instruction-set
+   verifier
    libbpf/index
    btf
    faq
@@ -34,4 +33,4 @@ that goes into great technical depth about the BPF Architecture.
    * :ref:`genindex`
 
 .. Links:
-.. _BPF and XDP Reference Guide: https://docs.cilium.io/en/latest/bpf/
\ No newline at end of file
+.. _BPF and XDP Reference Guide: https://docs.cilium.io/en/latest/bpf/