It works this way :
Physical joystick/gamepad has these controls :

gamepad – allows to bind keyboard keys and 2 axis (not full range, only edges -1.0, 0.0 and 1.0)
left stick – allows to bind keyboard keys, mouse and 2axis with full range from -1.0 to 1.0
right stick – the same like above

left and right stick shares 2axis settings. Keypad settings are unique per gamepad, left and right stick.

Left/right sticks are commonly named left/right joysticks. This was what I meant.

But reading again your post I start thinking that you want connect two physical gamepads to android device. Is it right? Unfortunately this is not implemented now. But you are second who requested it. Question is – is it possible? I will explain why I am asking. Android works this way :

If you touch down screen with your finger then you start mouse dragging. Now if you click with physical mouse then happens this :

1. android send cancel event (something like touch up) for touchscreen.
2. physical mouse does mouse down and up. And your finger is still down on your screen.

This means that android does not allow cooperation of two different components.
But maybe for joystick is it fixed. This must be tested.

Here I found a bit another problem
http://stackoverflow.com/questions/33070114/multiple-game-controllers-on-android

Or maybe you want assign to left stick 1st axis and to second stick 2nd axis. So you will have to different axis on each stick. Please what you need from above?

Thank you,
Tony