Submitting plugin to wordpress.org repository is a cautious as well as watchful process. Before submitting, one must have readme.txt and license (GPL 2 or later) in the plugin folder.
The plugin folder structure depends upon the coding style of the developer so it can be of different type. But, an important thing to note is that there must be the two files: readme.txt and license.txt. A standard readme.txt file can be seen in: