With some @ThinkJet tricks your query may look like this
with x as (
select
xmltype('
<workplaces>
<workspace>
<title>workspace1</title>
<item>
<day>1</day>
<openingTime>8:00</openingTime>
<closingTime>12:00</closingTime>
</item>
<item>
<day>1</day>
<openingTime>13:00</openingTime>
<closingTime>18:00</closingTime>
</item>
</workspace>
<workspace>
<title>workspace2</title>
<item>
<day>1</day>
<openingTime>9:00</openingTime>
<closingTime>14:00</closingTime>
</item>
<item>
<day>3</day>
<openingTime>12:00</openingTime>
<closingTime>16:00</closingTime>
</item>
</workspace>
</workplaces>
') xfield
from dual
)
SELECT "day", "openingTime", "closingTime"
FROM xmltable('$doc//workspace[title=$workspace_filter]/item'
passing (select xfield from x) as "doc",
('workspace1') as "workspace_filter"
columns "openingTime" path '//openingTime',
"closingTime" path '//closingTime',
"day" path '//day')