Add FWU booting instructions to the user guide

FWU uses additional images that have to be loaded,
and this patch adds the documentation of how to do
it in FVP and Juno.

Change-Id: I1a40641c11c5a4c8db0aadeaeb2bec30c9279e28
Signed-off-by: Roberto Vargas <roberto.vargas@arm.com>

docs/user-guide.rst

@@ -1205,6 +1205,56 @@ The resulting BL1 and FIP images may be found in:
     ./build/fvp/release/bl1.bin
     ./build/fvp/release/fip.bin
 
+
+Booting Firmware Update images
+-------------------------------------
+
+When Firmware Update (FWU) is enabled there are at least 2 new images
+that have to be loaded, the Non-Secure FWU ROM (NS-BL1U), and the
+FWU FIP.
+
+Juno
+~~~~
+
+The new images must be programmed in flash memory by adding
+an entry in the ``SITE1/HBI0262x/images.txt`` configuration file
+on the Juno SD card (where ``x`` depends on the revision of the Juno board).
+Refer to the `Juno Getting Started Guide`_, section 2.3 "Flash memory
+programming" for more information. User should ensure these do not
+overlap with any other entries in the file.
+
+::
+
+	NOR10UPDATE: AUTO                       ;Image Update:NONE/AUTO/FORCE
+	NOR10ADDRESS: 0x00400000                ;Image Flash Address [ns_bl2u_base_address]
+	NOR10FILE: \SOFTWARE\fwu_fip.bin        ;Image File Name
+	NOR10LOAD: 00000000                     ;Image Load Address
+	NOR10ENTRY: 00000000                    ;Image Entry Point
+
+	NOR11UPDATE: AUTO                       ;Image Update:NONE/AUTO/FORCE
+	NOR11ADDRESS: 0x03EB8000                ;Image Flash Address [ns_bl1u_base_address]
+	NOR11FILE: \SOFTWARE\ns_bl1u.bin        ;Image File Name
+	NOR11LOAD: 00000000                     ;Image Load Address
+
+The address ns_bl1u_base_address is the value of NS_BL1U_BASE - 0x8000000.
+In the same way, the address ns_bl2u_base_address is the value of
+NS_BL2U_BASE - 0x8000000.
+
+FVP
+~~~
+
+The additional fip images must be loaded with:
+
+::
+
+    --data cluster0.cpu0="<path_to>/ns_bl1u.bin"@0x0beb8000	[ns_bl1u_base_address]
+    --data cluster0.cpu0="<path_to>/fwu_fip.bin"@0x08400000	[ns_bl2u_base_address]
+
+The address ns_bl1u_base_address is the value of NS_BL1U_BASE.
+In the same way, the address ns_bl2u_base_address is the value of
+NS_BL2U_BASE.
+
+
 EL3 payloads alternative boot flow
 ----------------------------------