MAINTAINERS: add entry for ethtool

Michal did an amazing job converting ethtool to Netlink, but never
added an entry to MAINTAINERS for himself. Create a formal entry
so that we can delegate (portions) of this code to folks.

Over the last 3 years majority of the reviews have been done by
Andrew and I. I suppose Michal didn't want to be on the receiving
end of the flood of patches.

Reviewed-by: Simon Horman <horms@kernel.org>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Link: https://patch.msgid.link/20250204215729.168992-1-kuba@kernel.org
Signed-off-by: Paolo Abeni <pabeni@redhat.com>

Author: kuba-moo

MAINTAINERS

@@ -16455,6 +16455,16 @@ F:	include/net/dsa.h
 F:	net/dsa/
 F:	tools/testing/selftests/drivers/net/dsa/
 
+NETWORKING [ETHTOOL]
+M:	Andrew Lunn <andrew@lunn.ch>
+M:	Jakub Kicinski <kuba@kernel.org>
+F:	Documentation/netlink/specs/ethtool.yaml
+F:	Documentation/networking/ethtool-netlink.rst
+F:	include/linux/ethtool*
+F:	include/uapi/linux/ethtool*
+F:	net/ethtool/
+F:	tools/testing/selftests/drivers/net/*/ethtool*
+
 NETWORKING [GENERAL]
 M:	"David S. Miller" <davem@davemloft.net>
 M:	Eric Dumazet <edumazet@google.com>