This patch adds a description of the stm_source device class, an interface for the kernel code to send traces over STM devices. Cc: linux-api@vger.kernel.org Cc: Chunyan Zhang <zhang.chunyan@linaro.org> Cc: Mathieu Poirier <mathieu.poirier@linaro.org> Signed-off-by: Alexander Shishkin <alexander.shishkin@linux.intel.com>