MAINTAINERS: add a sample ethtool section entry

I feel like we don't do a good enough keeping authors of driver
APIs around. The ethtool code base was very nicely compartmentalized
by Michal. Establish a precedent of creating MAINTAINERS entries
for "sections" of the ethtool API. Use Andrew and cable test as
a sample entry. The entry should ideally cover 3 elements:
a core file, test(s), and keywords. The last one is important
because we intend the entries to cover core code *and* reviews
of drivers implementing given API!

Signed-off-by: Jakub Kicinski <[email protected]>
Reviewed-by: Simon Horman <[email protected]>
Link: https://patch.msgid.link/[email protected]
Signed-off-by: Paolo Abeni <[email protected]>

Author: kuba-moo

MAINTAINERS

@@ -16465,6 +16465,12 @@ F:	include/uapi/linux/ethtool*
 F:	net/ethtool/
 F:	tools/testing/selftests/drivers/net/*/ethtool*
 
+NETWORKING [ETHTOOL CABLE TEST]
+M:	Andrew Lunn <[email protected]>
+F:	net/ethtool/cabletest.c
+F:	tools/testing/selftests/drivers/net/*/ethtool*
+K:	cable_test
+
 NETWORKING [GENERAL]
 M:	"David S. Miller" <[email protected]>
 M:	Eric Dumazet <[email protected]>