I had gone deeper as mentioned before.
I created
Code
evdev:input:b0003v2052p0121e0101*
keyboard:usb:v2052p0121e0101*
KEYBOARD_KEY_0c00ea=volumedown
KEYBOARD_KEY_070051=volumedown
KEYBOARD_KEY_0c00ea did not work.
Could you please do this simple test. It will not take long. Please install Keymap Editor Addon and hit SETTINGS to assign to something. See if it registers. For this test you don't need to delete your keyboard.xml or hwdb file. Just installing the addon and seeing what happens.