doc: Split the User Guide into multiple files

The User Guide document has grown organically over time and
now covers a wide range of topics, making it difficult to
skim read and extract information from. Currently, it covers
these topics and maybe a couple more:

- Requirements (hardware, tools, libs)
- Checking out the repo
- Basic build instructions
- A comprehensive list of build flags
- FIP packaging
- Building specifically for Juno
- Firmware update images
- EL3 payloads
- Preloaded BL33 boot flow
- Running on FVPs
- Running on Juno

I have separated these out into a few groups that become new
documents. Broadly speaking, build instructions for the tools,
for TF-A generally, and for specific scenarios are separated.
Content relating to specific platforms (Juno and the FVPs are
Arm-specific platforms, essentially) has been moved into the
documentation that is specific to those platforms, under
docs/plat/arm.

Change-Id: Ica87c52d8cd4f577332be0b0738998ea3ba3bbec
Signed-off-by: Paul Beesley <paul.beesley@arm.com>
diff --git a/docs/getting_started/tools-build.rst b/docs/getting_started/tools-build.rst
new file mode 100644
index 0000000..bb707cb
--- /dev/null
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+Building Supporting Tools
+=========================
+
+Building and using the FIP tool
+-------------------------------
+
+Firmware Image Package (FIP) is a packaging format used by TF-A to package
+firmware images in a single binary. The number and type of images that should
+be packed in a FIP is platform specific and may include TF-A images and other
+firmware images required by the platform. For example, most platforms require
+a BL33 image which corresponds to the normal world bootloader (e.g. UEFI or
+U-Boot).
+
+The TF-A build system provides the make target ``fip`` to create a FIP file
+for the specified platform using the FIP creation tool included in the TF-A
+project. Examples below show how to build a FIP file for FVP, packaging TF-A
+and BL33 images.
+
+For AArch64:
+
+.. code:: shell
+
+    make PLAT=fvp BL33=<path-to>/bl33.bin fip
+
+For AArch32:
+
+.. code:: shell
+
+    make PLAT=fvp ARCH=aarch32 AARCH32_SP=sp_min BL33=<path-to>/bl33.bin fip
+
+The resulting FIP may be found in:
+
+::
+
+    build/fvp/<build-type>/fip.bin
+
+For advanced operations on FIP files, it is also possible to independently build
+the tool and create or modify FIPs using this tool. To do this, follow these
+steps:
+
+It is recommended to remove old artifacts before building the tool:
+
+.. code:: shell
+
+    make -C tools/fiptool clean
+
+Build the tool:
+
+.. code:: shell
+
+    make [DEBUG=1] [V=1] fiptool
+
+The tool binary can be located in:
+
+::
+
+    ./tools/fiptool/fiptool
+
+Invoking the tool with ``help`` will print a help message with all available
+options.
+
+Example 1: create a new Firmware package ``fip.bin`` that contains BL2 and BL31:
+
+.. code:: shell
+
+    ./tools/fiptool/fiptool create \
+        --tb-fw build/<platform>/<build-type>/bl2.bin \
+        --soc-fw build/<platform>/<build-type>/bl31.bin \
+        fip.bin
+
+Example 2: view the contents of an existing Firmware package:
+
+.. code:: shell
+
+    ./tools/fiptool/fiptool info <path-to>/fip.bin
+
+Example 3: update the entries of an existing Firmware package:
+
+.. code:: shell
+
+    # Change the BL2 from Debug to Release version
+    ./tools/fiptool/fiptool update \
+        --tb-fw build/<platform>/release/bl2.bin \
+        build/<platform>/debug/fip.bin
+
+Example 4: unpack all entries from an existing Firmware package:
+
+.. code:: shell
+
+    # Images will be unpacked to the working directory
+    ./tools/fiptool/fiptool unpack <path-to>/fip.bin
+
+Example 5: remove an entry from an existing Firmware package:
+
+.. code:: shell
+
+    ./tools/fiptool/fiptool remove \
+        --tb-fw build/<platform>/debug/fip.bin
+
+Note that if the destination FIP file exists, the create, update and
+remove operations will automatically overwrite it.
+
+The unpack operation will fail if the images already exist at the
+destination. In that case, use -f or --force to continue.
+
+More information about FIP can be found in the :ref:`Firmware Design` document.
+
+.. _tools_build_cert_create:
+
+Building the Certificate Generation Tool
+----------------------------------------
+
+The ``cert_create`` tool is built as part of the TF-A build process when the
+``fip`` make target is specified and TBB is enabled (as described in the
+previous section), but it can also be built separately with the following
+command:
+
+.. code:: shell
+
+    make PLAT=<platform> [DEBUG=1] [V=1] certtool
+
+For platforms that require their own IDs in certificate files, the generic
+'cert_create' tool can be built with the following command. Note that the target
+platform must define its IDs within a ``platform_oid.h`` header file for the
+build to succeed.
+
+.. code:: shell
+
+    make PLAT=<platform> USE_TBBR_DEFS=0 [DEBUG=1] [V=1] certtool
+
+``DEBUG=1`` builds the tool in debug mode. ``V=1`` makes the build process more
+verbose. The following command should be used to obtain help about the tool:
+
+.. code:: shell
+
+    ./tools/cert_create/cert_create -h
+
+--------------
+
+*Copyright (c) 2019, Arm Limited. All rights reserved.*