doc: dev-tools: kselftest.rst: update contributing new tests

Add a description that kernel config options should be added into a
config file that is placed next to the newly added test.
Signed-off-by: Anders Roxell <anders.roxell@linaro.org>
Reviewed-by: Shuah Khan (Samsung OSG) <shuah@kernel.org>
Signed-off-by: Jonathan Corbet <corbet@lwn.net>

Documentation/dev-tools/kselftest.rst

@@ -156,6 +156,11 @@ Contributing new tests (details)
    installed by the distro on the system should be the primary focus to be able
    to find regressions.
 
+ * If a test needs specific kernel config options enabled, add a config file in
+   the test directory to enable them.
+
+   e.g: tools/testing/selftests/android/ion/config
+
 Test Harness
 ============