Documentation: networking: add OPEN Alliance 10BASE-T1x MAC-PHY serial interface

The IEEE 802.3cg project defines two 10 Mbit/s PHYs operating over a
single pair of conductors. The 10BASE-T1L (Clause 146) is a long reach
PHY supporting full duplex point-to-point operation over 1 km of single
balanced pair of conductors. The 10BASE-T1S (Clause 147) is a short reach
PHY supporting full / half duplex point-to-point operation over 15 m of
single balanced pair of conductors, or half duplex multidrop bus
operation over 25 m of single balanced pair of conductors.

Furthermore, the IEEE 802.3cg project defines the new Physical Layer
Collision Avoidance (PLCA) Reconciliation Sublayer (Clause 148) meant to
provide improved determinism to the CSMA/CD media access method. PLCA
works in conjunction with the 10BASE-T1S PHY operating in multidrop mode.

The aforementioned PHYs are intended to cover the low-speed / low-cost
applications in industrial and automotive environment. The large number
of pins (16) required by the MII interface, which is specified by the
IEEE 802.3 in Clause 22, is one of the major cost factors that need to be
addressed to fulfil this objective.

The MAC-PHY solution integrates an IEEE Clause 4 MAC and a 10BASE-T1x PHY
exposing a low pin count Serial Peripheral Interface (SPI) to the host
microcontroller. This also enables the addition of Ethernet functionality
to existing low-end microcontrollers which do not integrate a MAC
controller.
Reviewed-by: Andrew Lunn <andrew@lunn.ch>
Signed-off-by: Parthiban Veerasooran <Parthiban.Veerasooran@microchip.com>
Link: https://patch.msgid.link/20240909082514.262942-2-Parthiban.Veerasooran@microchip.comSigned-off-by: Jakub Kicinski <kuba@kernel.org>

Documentation/networking/index.rst

@@ -88,6 +88,7 @@ Contents:
    nexthop-group-resilient
    nf_conntrack-sysctl
    nf_flowtable
+   oa-tc6-framework
    openvswitch
    operstates
    packet_mmap

MAINTAINERS

@@ -17113,6 +17113,12 @@ L:	linux-rdma@vger.kernel.org
 S:	Supported
 F:	drivers/infiniband/ulp/opa_vnic
 
+OPEN ALLIANCE 10BASE-T1S MACPHY SERIAL INTERFACE FRAMEWORK
+M:	Parthiban Veerasooran <parthiban.veerasooran@microchip.com>
+L:	netdev@vger.kernel.org
+S:	Maintained
+F:	Documentation/networking/oa-tc6-framework.rst
+
 OPEN FIRMWARE AND FLATTENED DEVICE TREE
 M:	Rob Herring <robh@kernel.org>
 M:	Saravana Kannan <saravanak@google.com>