net: phylink: clarify where phylink should be used

Update the phylink documentation to make it clear that phylink is
designed to be used on the MAC facing side of the link, rather than
between a SFP and PHY.

Signed-off-by: Russell King <rmk+kernel@armlinux.org.uk>
Reviewed-by: Andrew Lunn <andrew@lunn.ch>
Signed-off-by: David S. Miller <davem@davemloft.net>

Documentation/networking/sfp-phylink.rst

@@ -8,7 +8,8 @@ Overview
 ========
 
 phylink is a mechanism to support hot-pluggable networking modules
-without needing to re-initialise the adapter on hot-plug events.
+directly connected to a MAC without needing to re-initialise the
+adapter on hot-plug events.
 
 phylink supports conventional phylib-based setups, fixed link setups
 and SFP (Small Formfactor Pluggable) modules at present.