#include <linux/fs.h>
#include <linux/cdev.h>

#define MY_MAJOR       42
#define MY_MAX_MINORS  5

struct my_device_data {
    struct cdev cdev;
    /* my data starts here */
    //...
};

struct my_device_data devs[MY_MAX_MINORS];

const struct file_operations my_fops = {
    .owner = THIS_MODULE,
    .open = my_open,
    .read = my_read,
    .write = my_write,
    .release = my_release,
    .unlocked_ioctl = my_ioctl
};

int init_module(void)
{
    int i, err;

    err = register_chrdev_region(MKDEV(MY_MAJOR, 0), MY_MAX_MINORS,
                                      "my_device_driver");
    if (err != 0) {
        /* report error */
        return err;
    }

    for(i = 0; i < MY_MAX_MINORS; i++) {
        /* initialize devs[i] fields */
        cdev_init(&devs[i].cdev, &my_fops);
        cdev_add(&devs[i].cdev, MKDEV(MY_MAJOR, i), 1);
    }

    return 0;
}