Add a brief blurb saying how and when the kunit_test_suite() macro
works to the usage documentation.

Signed-off-by: Brendan Higgins <redacted>
---
 Documentation/dev-tools/kunit/usage.rst | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/Documentation/dev-tools/kunit/usage.rst b/Documentation/dev-tools/kunit/usage.rst
index 3c3fe8b5feccf..961d3ea3ca19a 100644
--- a/Documentation/dev-tools/kunit/usage.rst
+++ b/Documentation/dev-tools/kunit/usage.rst

@@ -211,6 +211,11 @@ KUnit test framework.
 .. note::
    A test case will only be run if it is associated with a test suite.
 
+``kunit_test_suite(...)`` is a macro which tells the linker to put the specified
+test suite in a special linker section so that it can be run by KUnit either
+after late_init, or when the test module is loaded (depending on whether the