The search term refers to updating the Huawei CAM-L21 (a model in the Huawei Y5II / Y6II series) using a firmware file stored on an external microSD card .
If you search for this firmware, ensure the file is specifically for CAM-L21 (not CAM-L03 or CAM-L23). Using the wrong UPDATE.APP from an SD card will permanently hard-brick the phone because Huawei's dload method overwrites the bootloader. cam-l21 firmware sd card