[kirkstone,14/16] ref-manual: variables: add RECIPE_SYSROOT and RECIPE_SYSROOT_NATIVE

diff --git a/documentation/ref-manual/variables.rst b/documentation/ref-manual/variables.rst
index 38b13ecf8d..517c35d032 100644
--- a/documentation/ref-manual/variables.rst
+++ b/documentation/ref-manual/variables.rst
@@ -6456,6 +6456,39 @@  system and gives an overview of their function and contents.
       in the ":ref:`ref-manual/devtool-reference:checking on the upgrade status of a recipe`"
       section.
 
+   :term:`RECIPE_SYSROOT`
+      This variable points to the directory that holds all files populated from
+      recipes specified in :term:`DEPENDS`. As the name indicates,
+      think of this variable as a custom root (``/``) for the recipe that will be
+      used by the compiler in order to find headers and other files needed to complete
+      its job.
+
+      This variable is related to :term:`STAGING_DIR_HOST` or :term:`STAGING_DIR_TARGET`
+      according to the type of the recipe and the build target.
+
+      To better understand this variable, consider the following examples:
+
+      -  For ``#include <header.h>``, ``header.h`` should be in ``"${RECIPE_SYSROOT}/usr/include"``
+
+      -  For ``-lexample``, ``libexample.so`` should be in ``"${RECIPE_SYSROOT}/lib"``
+         or other library sysroot directories.
+
+      The default value is ``"${WORKDIR}/recipe-sysroot"``.
+      Do not modify it.
+
+   :term:`RECIPE_SYSROOT_NATIVE`
+      This is similar to :term:`RECIPE_SYSROOT` but the populated files are from
+      ``-native`` recipes. This allows a recipe built for the target machine to
+      use ``native`` tools.
+
+      This variable is related to :term:`STAGING_DIR_NATIVE`.
+
+      The default value is ``"${WORKDIR}/recipe-sysroot-native"``.
+      Do not modify it.
+
+   :term:`REPODIR`
+      See :term:`bitbake:REPODIR` in the BitBake manual.
+
    :term:`REQUIRED_DISTRO_FEATURES`
       When inheriting the
       :ref:`features_check <ref-classes-features_check>`
@@ -7690,10 +7723,15 @@  system and gives an overview of their function and contents.
             for ``-native`` recipes, as they make use of host headers and
             libraries.
 
+      Check :term:`RECIPE_SYSROOT` and :term:`RECIPE_SYSROOT_NATIVE`.
+
    :term:`STAGING_DIR_NATIVE`
       Specifies the path to the sysroot directory used when building
       components that run on the build host itself.
 
+      The default value is ``"${RECIPE_SYSROOT_NATIVE}"``,
+      check :term:`RECIPE_SYSROOT_NATIVE`.
+
    :term:`STAGING_DIR_TARGET`
       Specifies the path to the sysroot used for the system for which the
       component generates code. For components that do not generate code,