Paul Walker's Mom -- My Granddaughter's Mom's an Alcoholic -- I Want Guardianship

Paul Walker's mother just filed court documents asking for guardianship of Paul's 15-year-old daughter ... because the real mom has a serious drinking problem.

Cheryl Walker claims in her docs -- obtained by TMZ -- Meadow and her mom, Rebecca Soteros, are already living with her but Rebecca can't care for her daughter because of her alcoholism.

As we previously reported ... Rebecca has 2 DUIs -- one in 2003 and another last year. We're told Meadow moved from Hawaii -- where Rebecca lived -- to live with Paul 3 years before he died because of her mom's problems with alcohol.

Cheryl says she's more than qualified -- she's raised 4 kids, she's a registered nurse and is a loving person.

Paul had said in his will he wanted his mom to be Meadow's guardian ... so this is clearly in line with what he wanted.