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>

1 files changed, 14 insertions, 8 deletions

diff --git a/docs/components/romlib-design.rst b/docs/components/romlib-design.rst
index e0a028e46..d34b3cc58 100644
--- a/docs/components/romlib-design.rst
+++ b/docs/components/romlib-design.rst
@@ -115,21 +115,27 @@ Memory impact
 ~~~~~~~~~~~~~
 
 Using library at ROM will modify the memory layout of the BL images:
+
 - The ROM library needs a page aligned RAM section to hold the RW data. This
-   section is defined by the ROMLIB_RW_BASE and ROMLIB_RW_END macros.
-   On Arm platforms a section of 1 page (0x1000) is allocated at the top of SRAM.
-   This will have for effect to shift down all the BL images by 1 page.
+  section is defined by the ROMLIB_RW_BASE and ROMLIB_RW_END macros.
+  On Arm platforms a section of 1 page (0x1000) is allocated at the top of SRAM.
+  This will have for effect to shift down all the BL images by 1 page.
+
 - Depending on the functions moved to the ROM library, the size of the BL images
-   will be reduced.
-   For example: moving MbedTLS function into the ROM library reduces BL1 and
-   BL2, but not BL31.
+  will be reduced.
+  For example: moving MbedTLS function into the ROM library reduces BL1 and
+  BL2, but not BL31.
+
 - This change in BL images size can be taken into consideration to optimize the
-   memory layout when defining the BLx_BASE macros.
+  memory layout when defining the BLx_BASE macros.
 
 Build library at ROM
 ~~~~~~~~~~~~~~~~~~~~~
 
-The environment variable ``CROSS_COMPILE`` must be set as per the user guide.
+The environment variable ``CROSS_COMPILE`` must be set appropriately. Refer to
+:ref:`Performing an Initial Build` for more information about setting this
+variable.
+
 In the below example the usage of ROMLIB together with mbed TLS is demonstrated
 to showcase the benefits of library at ROM - it's not mandatory.