docs, bpf: Ensure IETF's BPF mailing list gets copied for ISA doc changes

Given BPF is increasingly being used beyond just the Linux kernel, with
implementations in NICs and other hardware, Windows, etc, there is an
ongoing effort to document and standardize parts of the existing BPF
infrastructure such as its ISA. As "source of truth" we decided some
time ago to rely on the in-tree documentation, in particular, starting
out with the Documentation/bpf/instruction-set.rst as a base for later
RFC drafts on the ISA. Therefore, we want to ensure that changes to that
document have bpf@ietf.org in Cc, so add a MAINTAINERS file entry with
a section on documents related to standardization efforts. For now, this
only relates to instruction-set.rst, and later additional files will be
added.

Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Cc: Dave Thaler <dthaler@microsoft.com>
Cc: bpf@ietf.org
Link: https://datatracker.ietf.org/doc/bofreq-thaler-bpf-ebpf/
Link: https://lore.kernel.org/r/57619c0dd8e354d82bf38745f99405e3babdc970.1676068387.git.daniel@iogearbox.net
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

MAINTAINERS

@@ -4023,6 +4023,12 @@ L:	bpf@vger.kernel.org
 S:	Maintained
 F:	tools/testing/selftests/bpf/
 
+BPF [DOCUMENTATION] (Related to Standardization)
+L:	bpf@vger.kernel.org
+L:	bpf@ietf.org
+S:	Maintained
+F:	Documentation/bpf/instruction-set.rst
+
 BPF [MISC]
 L:	bpf@vger.kernel.org
 S:	Odd Fixes