junitxml: add properties node in testsuite level

The commit allow users to add a properties node in testsuite level see
example below:

<testsuite errors="0" failures="0" name="pytest" skips="1" tests="1"
time="11.824">
  <properties>
    <property name="ARCH" value="PPC"/>
    <property name="OS" value="RHEL 7.2"/>
    <property name="TestPlanURL" value="https://url.."/>
    <property name="Automated" value="True"/>
  </properties>
  <testcase classname="git.....>
  </testcase>
</testsuite>

The current situation is that properties node can be added to every
testcase node. However, sometimes we need some global properties that
applies to all testcases and give better description for the testsuite
itself.

doc/en/usage.rst

@@ -193,6 +193,53 @@ This will add an extra property ``example_key="1"`` to the generated
     Also please note that using this feature will break any schema verification.
     This might be a problem when used with some CI servers.
 
+LogXML: add_global_property
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+.. versionadded:: 2.10
+
+If you want to add a properties node in the testsuite level, which may contains properties that are relevant
+to all testcases you can use ``LogXML.add_global_properties``
+
+.. code-block:: python
+
+    import pytest
+
+    @pytest.fixture(scope="session")
+    def log_global_env_facts(f):
+
+        if pytest.config.pluginmanager.hasplugin('junitxml'):
+            my_junit = getattr(pytest.config, '_xml', None)
+
+        my_junit.add_global_property('ARCH', 'PPC')
+        my_junit.add_global_property('STORAGE_TYPE', 'CEPH')
+
+    @pytest.mark.usefixtures(log_global_env_facts)
+    def start_and_prepare_env():
+        pass
+
+    class TestMe:
+        def test_foo(self):
+            assert True
+
+This will add a property node below the testsuite node to the generated xml:
+
+.. code-block:: xml
+
+    <testsuite errors="0" failures="0" name="pytest" skips="0" tests="1" time="0.006">
+      <properties>
+        <property name="ARCH" value="PPC"/>
+        <property name="STORAGE_TYPE" value="CEPH"/>
+      </properties>
+      <testcase classname="test_me.TestMe" file="test_me.py" line="16" name="test_foo" time="0.000243663787842"/>
+    </testsuite>
+
+.. warning::
+
+    This is an experimental feature, and its interface might be replaced
+    by something more powerful and general in future versions. The
+    functionality per-se will be kept.
+
 Creating resultlog format files
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