manuals: document NVDCVE_API_KEY variable

Add brief documentation of NVDCVE_API_KEY variable, that was added
in 4.2.3, and emphasize that its use results in lower NVD API request
times.

(From yocto-docs rev: 9c7b452441bad2d7c929383d4665dfddb8f7ea72)

Signed-off-by: Noe Galea <ngalea@thegoodpenguin.co.uk>
Reviewed-by: Michael Opdenacker <michael.opdenacker@bootlin.com>
Reviewed-by: Andrew Murray <amurray@thegoodpenguin.co.uk>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

1 files changed, 15 insertions, 0 deletions

diff --git a/documentation/ref-manual/variables.rst b/documentation/ref-manual/variables.rst
index 3f37f42f21..6b5b5c0762 100644
--- a/documentation/ref-manual/variables.rst
+++ b/documentation/ref-manual/variables.rst
@@ -5585,6 +5585,21 @@ system and gives an overview of their function and contents.
 
          NON_MULTILIB_RECIPES = "grub grub-efi make-mod-scripts ovmf u-boot"
 
+   :term:`NVDCVE_API_KEY`
+      The NVD API key used to retrieve data from the CVE database when
+      using :ref:`ref-classes-cve-check`.
+
+      By default, no API key is used, which results in larger delays between API
+      requests and limits the number of queries to the public rate limits posted
+      at the `NVD developer's page <https://nvd.nist.gov/developers/start-here>`__.
+      
+      NVD API keys can be requested through the
+      `Request an API Key <https://nvd.nist.gov/developers/request-an-api-key>`__
+      page. You can set this variable to the NVD API key in your ``local.conf`` file.
+      Example::
+
+          NVDCVE_API_KEY = "fe753&7a2-1427-347d-23ff-b2e2b7ca5f3"
+
    :term:`OBJCOPY`
       The minimal command and arguments to run ``objcopy``.