Why there is seven i2c device nodes in /dev directory?

Hi All,

I found there are only three i2c devices(i2c0, i2c1, i2c2) in Product Design Guide. Then what do the device nodes below stand for on the Nano dev kit?

sercomm:~/spi_test$  ls /dev/ |grep -i i2c
i2c-0
i2c-1
i2c-2
i2c-3
i2c-4
i2c-5
i2c-6
sercomm:~/spi_test$ cat /proc/devices |grep -i i2c
 89 i2c

Thanks

@garretzou
The chip design 7 i2c bus, however the design may tell the carrier board design.