There is no notation for that.
In general, stty (and the OS components which use these settings) doesn't see keys as such – the terminal app translates those keys to a byte sequence and the tty layer only sees those translated bytes, and stty lets you se a specific byte which will make the tty layer trigger the interrupt signal.
In other words, the intr parameter is a single byte value corresponding to some symbol you can actually enter. (In the early Unix systems intr was set to the
So when you set intr to
^C, that's just stty shorthand for byte 0x03 (compare: the letter
C is 0x43 in ASCII). Basically both Shift and Ctrl just set and clear some bits of the 'base' byte. There's no such equivalent for Super, however.
As a result, most terminals merely ignore Super and send the base letter unmodified; some might send ANSI "escape" sequences (similar to those you get from arrow keys or function keys), but you couldn't use those with stty anyway because it still requires a single byte. You cannot bind the interrupt key to a multibyte sequence; it'd just pick up the first byte.
So the only thing you can do is somehow hack the terminal app itself to send a 0x03 byte when it receives the Super+C keypress. Some terminal emulators support this via generic "keyboard shortcuts", others might need actual source code patches.