net: dsa: Use conduit and user terms

Use more inclusive terms throughout the DSA subsystem by moving away
from "master" which is replaced by "conduit" and "slave" which is
replaced by "user". No functional changes.

Acked-by: Rob Herring <robh@kernel.org>
Acked-by: Stephen Hemminger <stephen@networkplumber.org>
Reviewed-by: Vladimir Oltean <vladimir.oltean@nxp.com>
Signed-off-by: Florian Fainelli <florian.fainelli@broadcom.com>
Link: https://lore.kernel.org/r/20231023181729.1191071-2-florian.fainelli@broadcom.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

Documentation: net: dsa: transition to the rst format

This patch also performs some minor adjustments such as numbering for
the receive path sequence, conversion of keywords to inline literals and
adding an index page so it looks better in the output of 'make htmldocs'.

Signed-off-by: Ioana Ciornei <ciorneiioana@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>