The driver is intended to work on both low-end (EP9301, EP9302) devices with 5-channel ADC and high-end (EP9307, EP9312, EP9315) devices with 10-channel touchscreen/ADC module.
Numbering scheme for channels 0..4 is defined in EP9301 and EP9302 datasheets. EP9307, EP9312 and EP9312 have 3 channels more (total 8), but the numbering is not defined. So the last three are numbered randomly, let's say.
Assuming ep93xx_adc is IIO device0, you'd find the following entries under /sys/bus/iio/devices/iio:device0/:
sysfs entry ball/pin name in_voltage0_raw YM in_voltage1_raw SXP in_voltage2_raw SXM in_voltage3_raw SYP in_voltage4_raw SYM in_voltage5_raw XP in_voltage6_raw XM in_voltage7_raw YP