What is language planning?
who plans what, for whom and how?
The only meaning of this term that I know is that language planning is the process of consciously shaping the way language is used (and what language or languages are used) in a country.
This can happen in a number of ways, but language planning is always done by governmental authorities. The authorities determine what languages are to be used, how they are to be written, and even what words are to be recognized and approved of.
The question of "for whom" is decided by politics. Language planning might be done to help linguistic minorities or it might be done to preserve the language and culture of the majority.
Language planning is a promotion of a unified administrative language or languages,official and government-level activity concerning the selection. It represents a coherent effort by individuals, groups, or organizations to influence language use or development.
Language policy and planning decisions arise in response to sociopolitical needs. Language planning decisions may be required, for example, where a number of linguistic groups compete for access to the mechanisms of day-to-day life, or where a particular linguistic minority is denied access to such mechanisms.