Purpose : Replace <p> to <div>+<br/>
Version: 4.X , File : /config/tinyMceConfig.config
Add TinyMCE configuration key under the <customConfig> element.
<config key="force_p_newlines">false</config>
<config key="force_br_newlines">true</config>
<config key="forced_root_block">div</config>
Recycle Application pool.