It's pretty straightforward but requires that you have some basic understanding on how a linux system is maintained.

Requirements, You need to be running open mode, inception is not enough with this.

• 1.) You need to boot the device in rescue mode, and back up the data from your root, home and Mydocs with tar.
• 2.) Then repartition the mmcblk with fdisk, and format the new partitions. MyDocs is normally formatted as fat while other partitions are ext2fs, but if you never mount your device to a windows machine you can also format MyDocs as ext2, which is a bit faster.
• 3.) After formatting the partitions, just restore the backups to the device and you are done.