Craft\NeoFieldType::validate PHP Method

    public function validate($blocks)
    {
        $errors = [];
        $blocksValidate = true;
        foreach ($blocks as $block) {
            if (!craft()->neo->validateBlock($block)) {
                $blocksValidate = false;
            }
        }
        if (!$blocksValidate) {
            $errors[] = Craft::t("Correct the errors listed above.");
        }
        $maxBlocks = $this->getSettings()->maxBlocks;
        if ($maxBlocks && count($blocks) > $maxBlocks) {
            if ($maxBlocks == 1) {
                $errors[] = Craft::t("There can’t be more than one block.");
            } else {
                $errors[] = Craft::t("There can’t be more than {max} blocks.", ['max' => $maxBlocks]);
            }
        }
        // TODO validate individual blocktype max blocks
        return $errors ? $errors : true;
    }