docs: networking: reorganize driver documentation again

Organize driver documentation by device type. Most documents
have fairly verbose yet uninformative names, so let users
first select a well defined device type, and then search for
a particular driver.

While at it rename the section from Vendor drivers to
Hardware drivers. This seems more accurate, besides people
sometimes refer to out-of-tree drivers as vendor drivers.

Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Acked-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>
Acked-by: Shannon Nelson <snelson@pensando.io>
Signed-off-by: David S. Miller <davem@davemloft.net>

Documentation/networking/device_drivers/cellular/index.rst

@@ -0,0 +1,18 @@
+.. SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
+
+Cellular Modem Device Drivers
+=============================
+
+Contents:
+
+.. toctree::
+   :maxdepth: 2
+
+   qualcomm/rmnet
+
+.. only::  subproject and html
+
+   Indices
+   =======
+
+   * :ref:`genindex`

Documentation/networking/device_drivers/cellular/qualcomm/rmnet.rst

@@ -0,0 +1,95 @@
+.. SPDX-License-Identifier: GPL-2.0
+
+============
+Rmnet Driver
+============
+
+1. Introduction
+===============
+
+rmnet driver is used for supporting the Multiplexing and aggregation
+Protocol (MAP). This protocol is used by all recent chipsets using Qualcomm
+Technologies, Inc. modems.
+
+This driver can be used to register onto any physical network device in
+IP mode. Physical transports include USB, HSIC, PCIe and IP accelerator.
+
+Multiplexing allows for creation of logical netdevices (rmnet devices) to
+handle multiple private data networks (PDN) like a default internet, tethering,
+multimedia messaging service (MMS) or IP media subsystem (IMS). Hardware sends
+packets with MAP headers to rmnet. Based on the multiplexer id, rmnet
+routes to the appropriate PDN after removing the MAP header.
+
+Aggregation is required to achieve high data rates. This involves hardware
+sending aggregated bunch of MAP frames. rmnet driver will de-aggregate
+these MAP frames and send them to appropriate PDN's.
+
+2. Packet format
+================
+
+a. MAP packet (data / control)
+
+MAP header has the same endianness of the IP packet.
+
+Packet format::
+
+  Bit             0             1           2-7      8 - 15           16 - 31
+  Function   Command / Data   Reserved     Pad   Multiplexer ID    Payload length
+  Bit            32 - x
+  Function     Raw  Bytes
+
+Command (1)/ Data (0) bit value is to indicate if the packet is a MAP command
+or data packet. Control packet is used for transport level flow control. Data
+packets are standard IP packets.
+
+Reserved bits are usually zeroed out and to be ignored by receiver.
+
+Padding is number of bytes to be added for 4 byte alignment if required by
+hardware.
+
+Multiplexer ID is to indicate the PDN on which data has to be sent.
+
+Payload length includes the padding length but does not include MAP header
+length.
+
+b. MAP packet (command specific)::
+
+    Bit             0             1           2-7      8 - 15           16 - 31
+    Function   Command         Reserved     Pad   Multiplexer ID    Payload length
+    Bit          32 - 39        40 - 45    46 - 47       48 - 63
+    Function   Command name    Reserved   Command Type   Reserved
+    Bit          64 - 95
+    Function   Transaction ID
+    Bit          96 - 127
+    Function   Command data
+
+Command 1 indicates disabling flow while 2 is enabling flow
+
+Command types
+
+= ==========================================
+0 for MAP command request
+1 is to acknowledge the receipt of a command
+2 is for unsupported commands
+3 is for error during processing of commands
+= ==========================================
+
+c. Aggregation
+
+Aggregation is multiple MAP packets (can be data or command) delivered to
+rmnet in a single linear skb. rmnet will process the individual
+packets and either ACK the MAP command or deliver the IP packet to the
+network stack as needed
+
+MAP header|IP Packet|Optional padding|MAP header|IP Packet|Optional padding....
+
+MAP header|IP Packet|Optional padding|MAP header|Command Packet|Optional pad...
+
+3. Userspace configuration
+==========================
+
+rmnet userspace configuration is done through netlink library librmnetctl
+and command line utility rmnetcli. Utility is hosted in codeaurora forum git.
+The driver uses rtnl_link_ops for communication.
+
+https://source.codeaurora.org/quic/la/platform/vendor/qcom-opensource/dataservices/tree/rmnetctl