doc: subsys: Add dfu and mgmt subsytem doc

Add documentation for two closely-related subystems: dfu and mgmt, which
are currently undocumented.

Signed-off-by: Carles Cufi <[email protected]>

Author: carlescufi

doc/subsystems/dfu.rst

@@ -0,0 +1,51 @@
+.. _dfu:
+
+Device Firmware Upgrade Subsystem
+#################################
+
+Overview
+********
+
+The Device Firmware Upgrade subsystem provides the necessary frameworks to
+upgrade the image of a Zephyr-based application at run time. It currently
+consists of two different modules:
+
+* :file:`boot/`: Interface code to bootloaders
+* :file:`img_util/`: Image management code
+
+The DFU subsystem deals with image management, but not with the transport
+or management protocols themselves required to send the image to the target
+device. For information on these protocols and frameworks please refer to the
+:ref:`mgmt` section.
+
+Bootloaders
+***********
+
+.. _mcuboot:
+
+MCUboot
+=======
+
+Zephyr is directly compatible with the open source, cross-RTOS `MCUboot`_ boot
+loader. It interfaces with MCUboot and is aware of the image format required
+by it, so that Device Firmware Upgrade is available when MCUboot is the boot
+loader used with Zephyr. The source code itself is hosted in the
+`MCUboot GitHub Project`_ page.
+
+In order to use MCUboot with Zephyr you need to take the following into account:
+
+1. You will need to define the :ref:`mcuboot_partitions` required by MCUboot in
+   the :ref:`flash_partitions`.
+2. Your application's :file:`.conf` file needs to enable the
+   :option:`CONFIG_BOOTLOADER_MCUBOOT` Kconfig option in order for Zephyr to
+   be built in an MCUboot-compatible manner
+3. You need to build and flash MCUboot itself on your device
+4. You might need to take precautions to avoid mass erasing the flash and also
+   to flash the Zephyr application image at the correct offset (right after the
+   bootloader)
+
+More detailed information regarding the use of MCUboot with Zephyr  can be found
+in the `MCUboot with Zephyr`_ documentation page on the MCUboot website.
+
+.. _MCUboot with Zephyr: https://mcuboot.com/mcuboot/readme-zephyr.html
+.. _MCUboot GitHub Project: https://github.com/runtimeco/mcuboot

doc/subsystems/mgmt.rst

@@ -0,0 +1,62 @@
+.. _mgmt:
+
+Management Subsystem
+####################
+
+Overview
+********
+
+The management subsystem allows remote management of Zephyr-enabled devices.
+The following management operations are available:
+
+* Image management
+* File System management
+* Log management (currently disabled)
+* OS management
+
+over the following transports:
+
+* BLE (Bluetooth Low Energy)
+* Serial (UART)
+
+The management subsystem is based on the Simple Management Protocol (SMP)
+provided by `MCUmgr`_, an open source project that provides a
+management subystem that is portable across multiple real-time operating
+systems.
+
+The management subsystem is split in two different locations in the Zephyr tree:
+
+* :file:`ext/lib/mgmt/mcumgr/` contains a clean import of the MCUmgr project
+* :file:`subsys/mgmt/` contains the Zephyr-specific bindings to MCUmgr
+
+Additionally there is a :ref:`sample <smp_svr_sample>` that provides management
+functionality over BLE and serial.
+
+.. _mcumgr_cli:
+
+Command-line Tool
+*****************
+
+MCUmgr provides a command-line tool, :file:`mcumgr`,for managing remote devices.
+The tool is written in the Go programming language.
+
+Installation information can be found in the `MCUmgr command-line tool`_
+section of the `MCUmgr documentation`_. A full rundown of the necessary commands
+to perform Device Firmware Upgrade is located in
+`MCUmgr command-line tool examples`_, and a practical step-by-step guide to DFU
+using MCUmgr can be found in :ref:`smp_svr_sample`.
+
+Bootloader integration
+**********************
+
+The :ref:`dfu` subsystem integrates the management subsystem with the
+bootloader, providing the ability to send and upgrade a Zephyr image to a
+device.
+
+Currently only the MCUboot bootloader is supported. See :ref:`mcuboot` for more
+information.
+
+.. _MCUmgr: https://github.com/apache/mynewt-mcumgr
+.. _MCUmgr documentation: https://github.com/apache/mynewt-mcumgr#mcumgr
+.. _MCUmgr command-line tool: https://github.com/apache/mynewt-mcumgr#command-line-tool
+.. _MCUmgr command-line tool examples: https://github.com/apache/mynewt-mcumgr-cli#examples

doc/subsystems/subsystems.rst

@@ -11,7 +11,9 @@ to applications.
 
    bluetooth/bluetooth.rst
    c_library
+   dfu
    logging/index
+   mgmt
    networking/networking.rst
    power_management.rst
    sensor