doc: add oneApi toolchain

Document how to use oneApi toolkit with Zephyr.

Signed-off-by: Anas Nashif <[email protected]>

Author: nashif

doc/getting_started/toolchain_3rd_party_x_compilers.rst

@@ -50,6 +50,26 @@ GNU ARM Embedded
       > echo %GNUARMEMB_TOOLCHAIN_PATH%
       C:\gnu_arm_embedded
 
+Intel oneApi Toolkits
+*********************
+
+#. Download `Intel oneAPI Base Toolkit
+   <https://software.intel.com/content/www/us/en/develop/tools/oneapi/all-toolkits.html>`_
+
+#. Assuming the toolkit is installed in ``/opt/intel/oneApi``, set environment
+   using::
+
+        export ONEAPI_TOOLCHAIN_PATH=/opt/intel/oneapi
+        source $ONEAPI_TOOLCHAIN_PATH/compiler/latest/env/vars.sh
+
+   To setup the complete oneApi environment, use::
+
+        source  /opt/intel/oneapi/setvars.sh
+
+   The above will also change the python environment to the one used by the
+   toolchain and might conflict with what Zephyr uses.
+
+#. Set :envvar:`ZEPHYR_TOOLCHAIN_VARIANT` to ``oneApi``.
 
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