container_of

/**

• container_of - cast a member of a structure out to the containing structure
• @ptr: the pointer to the member.
• @type: the type of the container struct this is embedded in.
• @member: the name of the member within the struct.

*/
#define container_of(ptr, type, member) ({
const typeof( ((type *)0)->member ) *__mptr = (ptr);
(type *)( (char *)__mptr - offsetof(type,member) );})

You can refer to the follow link about container_of
https://radek.io/2012/11/10/magical-container_of-macro/