convert_fromJSON(colWithJsonText)['cdrreasun']

SELECT ratinggrouplist
    ,t3.cdrlist3.cdrreason AS cdrreason
    ,t3.cdrlist3.cdrstart AS cdrstart
    ,t3.cdrlist3.cdrend AS cdrend
    ,t3.cdrlist3.cdrduration AS cdrduration
FROM (
    SELECT ratinggrouplist, convert_from(t2.cdrlist2.`element`, 'JSON') AS cdrlist3
    FROM (
        SELECT ratinggrouplist ,flatten(t1.cdrlist1.`value`) AS cdrlist2
        FROM (
            SELECT ratinggrouplist, kvgen(cdrlist) AS cdrlist1
            FROM dfs.tmp.SOME_TABLE
            ) AS t1
        ) AS t2
    ) AS t3;