doc: Use proper note and warning annotations

The documentation contains plenty of notes and warnings. Enable
special rendering of these blocks by converting the note prefix
into a .. note:: annotation.

Change-Id: I34e26ca6bf313d335672ab6c2645741900338822
Signed-off-by: Paul Beesley <paul.beesley@arm.com>
diff --git a/docs/getting_started/porting-guide.rst b/docs/getting_started/porting-guide.rst
index 5be8c15..94ec932 100644
--- a/docs/getting_started/porting-guide.rst
+++ b/docs/getting_started/porting-guide.rst
@@ -331,7 +331,9 @@
 
    SCP_BL2U image identifier, used by BL1 to fetch an image descriptor
    corresponding to SCP_BL2U.
-   NOTE: TF-A does not provide source code for this image.
+
+   .. note::
+      TF-A does not provide source code for this image.
 
 If the Non-Secure Firmware Updater ROM, NS_BL1U is used, the following must
 also be defined:
@@ -340,7 +342,9 @@
 
    Defines the base address in non-secure ROM where NS_BL1U executes.
    Must be aligned on a page-size boundary.
-   NOTE: TF-A does not provide source code for this image.
+
+   .. note::
+      TF-A does not provide source code for this image.
 
 -  **#define : NS_BL1U_IMAGE_ID**
 
@@ -354,7 +358,9 @@
 
    Defines the base address in non-secure memory where NS_BL2U executes.
    Must be aligned on a page-size boundary.
-   NOTE: TF-A does not provide source code for this image.
+
+   .. note::
+      TF-A does not provide source code for this image.
 
 -  **#define : NS_BL2U_IMAGE_ID**
 
@@ -1000,8 +1006,9 @@
 and must be implemented in assembly because it may be called before the C
 environment is initialized.
 
-Note: The address from where it was called is stored in x30 (Link Register).
-The default implementation simply spins.
+.. note::
+   The address from where it was called is stored in x30 (Link Register).
+   The default implementation simply spins.
 
 Function : plat_get_bl_image_load_info()
 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
@@ -1042,9 +1049,10 @@
 value as part of the attack most of the time. Therefore, it should return a
 true random number.
 
-Note: For the protection to be effective, the global data need to be placed at
-a lower address than the stack bases. Failure to do so would allow an attacker
-to overwrite the canary as part of the stack buffer overflow attack.
+.. warning::
+   For the protection to be effective, the global data need to be placed at
+   a lower address than the stack bases. Failure to do so would allow an
+   attacker to overwrite the canary as part of the stack buffer overflow attack.
 
 Function : plat_flush_next_bl_params()
 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
@@ -2564,10 +2572,12 @@
 output to be routed over the normal console infrastructure and get printed on
 consoles configured to output in crash state. ``console_set_scope()`` can be
 used to control whether a console is used for crash output.
-NOTE: Platforms are responsible for making sure that they only mark consoles for
-use in the crash scope that are able to support this, i.e. that are written in
-assembly and conform with the register clobber rules for putc() (x0-x2, x16-x17)
-and flush() (x0-x3, x16-x17) crash callbacks.
+
+.. note::
+   Platforms are responsible for making sure that they only mark consoles for
+   use in the crash scope that are able to support this, i.e. that are written
+   in assembly and conform with the register clobber rules for putc()
+   (x0-x2, x16-x17) and flush() (x0-x3, x16-x17) crash callbacks.
 
 In some cases (such as debugging very early crashes that happen before the
 normal boot console can be set up), platforms may want to control crash output